Labelled elastase inhibitors

ABSTRACT

A human leucocyte elastase (HLE) inhibitor labelled with a detector moiety where the inhibitor is synthetic and has a molecular weight of less than 2000, is useful for the diagnostic imaging of sites of inflammation of infection in vivo, for labelling leucocytes in vitro, or for radiotherapy of rthritis. The HLE inhibitor is preferably a β-lactam or an azetidinone.

This a 371 of PCT/GB97/02467, filed on Sep. 10, 1997.

The present invention relates to a class of compounds useful in the diagnosis or radiotherapy of infection, inflammation or thrombi, pharmaceutical formulations containing them, their use in diagnosis of disease and methods for their preparation.

Diagnostic imaging of infection or inflammation in clinical practice typically uses either the radiopharmaceutical ⁶⁷Ga citrate, or radiolabelled white blood cells (leucocytes) since leucocytes are known to accumulate at sites of infection/inflammation. ¹¹¹In or ^(99m)Tc are the radioisotopes normally used to label leucocytes.

Labelled leucocytes have become the method of choice in current clinical practice for the diagnostic imaging of sites of infection/inflammation. With the favourable imaging characteristics of ^(99m)Tc, the specificity of labelled leucocytes and good background clearance, this approach lends itself to the diagnosis of gut lesions such as inflammatory bowel disease or appendicitis. Such diseases cannot be diagnosed with non-specific agents due to the high gut background levels. The problem with the ex-vivo labelled leucocyte approach is that the current cell labelling agents used are non-specific. This means that the leucocytes have to be first separated from the excess red blood cells in blood taken from the patient to be imaged. The cell separation is a labour-intensive operation which requires a skilled operator to achieve efficient separation without compromising white cell integrity. There is also the intrinsic hazard associated with manipulation of blood samples. There has therefore been considerable interest in the field in developing an agent which could be used to image sites of infection which does not require this onerous cell separation prior to labelling and administration to the patient.

Human leucocyte elastase (HLE) is a powerful endopeptidase enzyme capable of hydrolysing amide bonds in a variety of proteins and peptides, including the structural proteins elastin, collagen and fibronectin [R L Stein et al, Ann. Rep. Med. Chem., 20, 237 (1985); P D Edwards and P R Bernstein, Med. Chem. Rev., 14, 127 (1994)]. At sites of infection or inflammation HLE is released by the activated leucocytes and causes tissue destruction. It is also known that leucocytes accumulate in thrombi and that elastase is released during blood coagulation. The released elastase has been shown to be important in fibrinogenlysis [E. F. Plow, J. Clin. Invest., 69, 564-572 (1982)].

EP 0595557 A1 (Merck) discloses that the following compounds are useful as HLE inhibitors for the treatment of inflammatory pathologies such as emphysema or rheumatoid arthritis:

where: R is C₁₋₆ alkyl;

R¹ is C₁₋₆ alkyl or C₁₋₆ alkoxy-C₁₋₆ alkyl;

M is H, C₁₋₆ alkyl, hydroxyalkyl, alkoxyalkyl, haloalkyl or C₂₋₆ alkenyl;

Ra and Rb are H, Hal, OH, Ph, COOH or C₁₋₆ alkyl, alkoxy or ester;

R² and R³ are H, Hal, COOH, Ph, OH, CN, amino, C₁₋₆ alkyl, alkoxy or ester, or amide

R⁴ is amide or ester with an optional alkyl spacer group.

Radio labelled HLE inhibitors have been little studied. Moser et al. [Am. J. Med., 84 (Suppl.6A), 70 (1988)] report that ¹³¹I-labelled α₁-antitrypsin persists in the human lung for up to one week post injection with little or no uptake in the liver or spleen. The paper does not, however, discuss potential applications of radiolabelled (α-antitrypsin. A tritium-labelled synthetic HLE inhibitor has been used to study the pharmacokinetics of the HLE inhibitor in rats and monkeys [J. B. Doherty et al, Proc. Nat. Acad. Sci. USA, 90, 8727-31 (1993)]. A ¹³C-labelled synthetic HLE inhibitor has been prepared to study the interaction of the inhibitor with HLE in vitro [B. G. Green et al, Biochem. 34, 14331-14355 (1995)]. Neither publication discloses the use of labelled HLE inhibitors for diagnostic imaging of infection, inflammation or thrombi nor are ³H or ¹³C suitable labelling moieties for external diagnostic imaging. Rusckowski et al [J. Nucl. Med., abstract P667 (1996)] report that a genetically engineered protein inhibitor of HLE named EPI-hNE-2 (molecular weight 6759) can be radiolabelled with ^(99m)Tc via a bifunctional chelate. The radiolabelled protein is reported to show some uptake in a mouse infection model. EPI-hNE-2 is an oligopeptide and could suffer from the same immunogenic problems as Fab′ or larger fragments of antibodies. Furthermore, the size of the molecule limits migration across cell membranes (e.g. those of granulocytes), hence intracellular HLE would not be targeted using this approach.

Blaszczak et al [J. Lab. Comp. Radiopharm., 27, 401-406 (1989)] have described the preparation of ¹²⁵I-radiolabelled penicillin V (i.e. a bicyclic β-lactam) for use in the in vitro assay of penicillin binding protein. There is no suggestion in the paper of in vivo imaging applications and ¹²⁵I would not be a preferred radioisotope for external imaging.

It has now been discovered that labelled synthetic HLE inhibitors are useful in the detection of sites of infection or inflammation. Use of a synthetic as opposed to a proteinaceous or polypeptide inhibitor has the significant advantages that the chemical nature of the agent can be fully defined, and potential concerns over immunogenicity are avoided. In addition the position of the label is known unambiguously, and unlike chemotactic peptides or interleukins, the labelled elastase inhibitor is not required to be of very high specific activity because there is an excess of elastase present both within granulocytes and at sites of infection/inflammation. The labelled HLE inhibitors are also useful in the detection of thrombi.

Thus the present invention relates to diagnostic agents for the detection of sites of infection or inflammation or thrombi in the human body. The agents comprise a synthetic human leucocyte elastase (HLE) inhibitor which has a molecular weight of less than 2000 Daltons and is labelled with a detectable moiety suitable for external imaging (e.g. by scintigraphy or MRI), such as a radionuclide or a paramagnetic metal ion. The agent acts by targeting HLE either within leucocytes (in vivo or in vitro), or at sites of HLE release such as sites of infection, inflammation or thrombi. Radiolabelled HLE inhibitors have been shown to selectively label human granulocytes in vitro and to target sites of infection/inflammation in vivo in an animal model of this pathology.

The “detectable moiety” is a substance suitable for external imaging after human administration such as a radionuclide which emits radiation that can penetrate soft tissue; a paramagnetic moiety as a contrast agent for MRI (e.g. certain metal ions such as gadolinium(III), or manganese(II)); a radiopaque moiety such as lopamidol for X-ray contrast imaging (computer assisted tomography ) or an ultrasound contrast agent. Preferably, the detectable moiety is a radionuclide which is either a positron emitter (such as ¹⁸F, ¹¹C, ¹⁵O, ¹³N, ⁶⁸Ga or ⁶⁴Cu) or a γ-emitter such as ¹²³I, ^(99m)Tc, ¹¹¹In, ¹¹³ m In or ⁶⁷Ga. Most preferred radionuclides are γ-emitters, especially ¹²³I and ^(99m)Tc. ³H and ¹⁴C do not have radioactive emissions suitable for external imaging and are therefore outside the scope of the present invention. It is also envisaged that certain radionuclides will confer useful radiotherapeutic properties on the labelled HLE inhibitors. Thus for example ⁹⁰Y, ⁸⁹Sr, ¹⁸⁶Re, ¹⁸⁸Re, ¹²⁵I or ¹³¹I labelled HLE inhibitors could be used in the treatment of rheumatoid arthritis and other bone infections/inflammations. In such applications the therapeutic effect would be due to the local targeted radioactive dose delivered to specific cells, as opposed to any pharmacological effect due to the inhibitor. Whichever detectable moiety is chosen, it is strongly preferred that it is bound to the synthetic HLE inhibitor in such a way that it does not undergo facile metabolism in blood (in vivo or in vitro) with the result that the biodistribution of the detectable moiety no longer reflects that of the HLE inhibitor.

The data presented herein demonstrate that radiolabelled synthetic HLE inhibitors offer a novel and convenient method for targeting sites of infection/inflammation or thrombosis. The mechanism is believed to involve binding to HLE present within circulating granulocytes in the bloodstream (which then concentrate at the site of pathology), or binding to free, extracellular HLE released at sites of pathology. Such a directly-injectable infection/inflammation imaging compound offers significant advantages over existing and proposed radiopharmaceuticals. The specificity for HLE means that the agents should, like ex vivo labelled leucocytes, be capable of imaging lesions associated with leucocyte infiltration such as appendicitis or inflammatory bowel disease. Use of a relatively small synthetic molecule means that the background clearance problems associated with macromolecules are avoided, and substituents can readily be varied in a controlled manner to adjust lipophilicity, plasma protein binding and rate of clearance.

The following classes of synthetic HLE inhibitor with a molecular weight of less than 2000 are suitable for the present invention:

Short chain (3-5 mer) peptides and peptide analogues (e.g. trifluoroacetyl peptides), hydrophobic inhibitors (e.g. elasnin and synthetic analogues).

Inhibitors against the active site histidine (e.g. peptide chloromethyl ketones).

Covalent inhibitors (e.g. peptide aldehydes, peptide ketones, halomethylketones, peptide boronic acids) and acylating agents (sulphonyl fluorides, aminoalkyl phosphono fluoridates, azapeptide nitrophenyl esters, activated carbamates and latent isocyanates, benzoxazin-4-ones, 3-alkoxyl-4-chloroisocoumarins, isatoic anhydrides, acyl saccharins).

Mechanism based inhibitors (e.g. chloropyrones and chloroisocoumarins, 7-amino-4-chloroisocoumarins, ynenol lactones and β-lactams).

Preferred HLE inhibitors for use in the present invention are the mechanism-based inhibitors, especially β-lactams which can be monocyclic (i.e. azetidinones) or have more than one fused ring (such as penicillins, cephalosporins or clavulanic acid analogues) and ynenol lactones. Most preferred are β-lactams, especially monocyclic β-lactams (i.e. azetidinones).

Preferred β-lactams are of formula:

Where R¹ is R⁸, XR⁸, (CRR)_(n)(C═X)R⁸ or (C═X)NR⁸ ₂

X is O or S

n is 0-3.

R⁸ is H, OH, a substituted or unsubstituted C₃₋₁₂ carbocyclic or heterocyclic ring which may be saturated or unsaturated, C₁₋₁₀ alkyl, C₃₋₁₂ aryl, C₄₋₁₂ alkylaryl, C₂₋₁₀ alkenyl, C₂₋₁₀ alkynyl, C₁₋₁₀ alkoxy, C₁₋₁₀ alkoxyalkyl, C₁₋₁₀ hydroxyalkyl, C₁₋₁₀ aminoalkyl, C₁₋₁₀ perfluoroalkyl, C₁₋₁₀ haloalkyl, C₁₋₁₀ carboxyalkyl, C₁₋₁₀ amidoalkyl or C₁₋₁₀ ketoalkyl.

R², R³ are the same or different and each H, C₁₋₄ alkyl, C₂₋₄ alkenyl, C₂₋₄ alkynyl, C₁₋₄ alkoxyalkyl, C₁₋₄ hydroxyalkyl, C₁₋₄ aminoalkyl, C₁₋₄ perfluoroalkyl, C₁₋₄ haloalkyl, Hal, C₁₋₄ carboxyalkyl, OR, SR, NRR (CH₂)_(n)CONRR, NR(CO)R or (CH₂)_(n)CO₂R.

R⁴ is a leaving group chosen from Hal, XR⁸, X(C═X)R⁸, OSOR⁸, OSO₂R⁸ OSO₂Hal, SOR⁸ SO₂R⁸ SO₂NR⁸ ₂ NRSO₂R, (C═X)R⁸, (C═X)NR⁸ ₂, (C═X)R⁸, NO₂, CN, PO_(n)R⁸ ₂ or XC₆H_(4−n) Y_(n)

Y is the same or different and is R, NO₂, Hal, CONR⁸ ₂, SO₂NR⁸ ₂ or CO₂R.

R⁵ is R or R⁴

R is the same or different and is H, C₁₋₄ alkyl, C₂₋₄ alkenyl, C₂₋₄ alkynyl, C₁₋₄ alkoxy, C₁₋₄ alkoxyalkyl, C₁₋₄ hydroxyalkyl, C₁₋₄ aminoalkyl, C₁₋₄ perfluoroalkyl, C₁₋₄ haloalkyl or C₁₋₄ carboxyalkyl.

whereby two or more of the groups R¹, R², R³, R⁴ and R₅ may be combined to form a substituted or unsubstituted carbocyclic or heterocyclic ring which may be saturated or unsaturated,

characterised in that the β-lactam contains or has covalently bonded thereto at least one detectable moiety, and with the proviso that when R⁴ is XR⁸, X is S and R¹ and R⁴ are combined to form a cyclic carboxyalkyl group, then the detectable moiety is not ¹²⁵I.

Preferred azetidinones are of formula:

Where R¹ is R⁸, XR⁸, (CRR)_(n)(C═X)R⁸ or (C═X)NR⁸ ₂

X is O or S

n is 0-3.

R⁸ is H, OH, a substituted or unsubstituted C₃₋₁₂ carbocyclic or heterocyclic ring which may be saturated or unsaturated, C₁₋₁₀ alkyl, C₃₋₁₂ aryl, C₄₋₁₂ alkyiaryl, C₂₋₁₀ alkenyl, C₂₋₁₀ alkynyl, C₁₋₁₀ alkoxy, C₁₋₁₀ alkoxyalkyl, C₁₋₁₀ hydroxyalkyl, C₁₋₁₀ aminoalkyl, C₁₋₁₀ perfluoroalkyl, C₁₋₁₀ haloalkyl, C₁₋₁₀ carboxyalkyl, C₁₋₁₀ amidoalkyl or C₁₋₁₀ ketoalkyl.

R², R³ are the same or different and each H, C₁₋₄ alkyl, C₂₋₄ alkenyl, C₂₋₄ alkynyl, C₁₋₄ alkoxyalkyl, C₁₋₄ hydroxyalkyl, C₁₋₄aminoalkyl, C₁₋₄ perfluoroalkyl, C₁₋₄ haloalkyl, Hal, C₁₋₄ carboxyalkyl, OR, SR, NRR (CH₂)_(n)CONRR, NR(CO)R or (CH₂)_(n)CO₂R.

R⁴ is a leaving group chosen from Hal, XR⁸, X(C═X)R⁸, OSOR⁸, OSO₂R⁸ OSO₂Hal, SOR⁸ SO₂R⁸, SO₂NR⁸ ₂ NRSO₂R, (C═X)R⁸, (C═X)NR⁸ ₂, (C═X)R⁸, NO₂, CN, PO_(n)R⁸ ₂ or XC₆H_(4−n)Y_(n)

Y is the same or different and is R, NO₂, Hal, CONR⁸ ₂, SO₂NR⁸ ₂ or CO₂R.

R⁵ is R or R⁴

R is the same or different and is H, C₁₋₄ alkyl, C₂₋₄ alkenyl, C₂₋₄ alkynyl, C₁₋₄ alkoxy, C₁₋₄ alkoxyalkyl, C₁₋₄ hydroxyalkyl, C₁₋₄ aminoalkyl, C₁₋₄ perfluoroalkyl, C₁₋₄ haloalkyl or C₁₋₄ carboxyalkyl.

characterised in that the azetidinone contains or has covalently

bonded thereto at least one detectable moiety.

Attachment of the detectable moiety at the R⁴ position is least preferred since this group is believed to be lost from the β-lactam as a consequence of covalent binding to the active site of the elastase enzyme. Groups R² and R³ on the β-lactam are responsible for binding to the S₁ site on the enzyme, and literature evidence suggests that these groups need to be relatively small (e.g. the size of an ethyl moiety). Hence it is likely that only a limited range of detectable moieties could be successfully attached at the R²/R³ positions. The detectable moiety is therefore most preferably attached at the R¹ position of the β-lactam or azetidinone.

Preferred R¹ groups are those of formula:

where R⁶ is an optionally substituted alkyl or phenyl group to which the detectable moiety is attached and R⁷ is H or a C₁₋₆ alkyl group.

When the detectable moiety is a radioactive or paramagnetic metal the metal is always chelated, i.e. a chelate-HLE inhibitor conjugate is used. Metal complexes of the HLE inhibitor alone (i.e. HLE inhibitors without at least one substituent which is designed to coordinate to metal atoms) are not part of the present invention. The term chelate-HLE conjugate covers the situations where the chelating agent is attached as a discrete chemical entity (i.e. as a single substituent on the HLE inhibitor), and when two or more metal donor atoms are attached as substituents at different positions on the HLE molecule. The chelate-HLE inhibitor conjugate is complexed with metal ions (such as technetium, gadolinium or yttrium) giving a metal complex of the chelating agent which is linked to the synthetic HLE inhibitor. The chelating agent is preferably polydentate and/or macrocyclic so that a stable metal complex is formed which can survive challenge by endogenous competing ligands for the metal in vivo such as transferrin or plasma proteins. When intracellular HLE is the target, the metal complex is preferably neutral since this facilitates transport of the labelled inhibitor conjugate across cell membranes such as those of granulocytes. When extracellular HLE released at sites of infection/inflammation or thrombi is the target then membrane permeability is of less importance and a charged metal complex may be desirable to facilitate background clearance. The metal complex should also preferably be of low lipophilicity (since high lipophilicity is often related to non-specific uptake), and exhibit low plasma protein binding (PPB) since plasma-bound label again contributes to undesirable high, non-specific blood background for the imaging agent.

Examples of suitable chelating agents for technetium are diaminedioximes (U.S. Pat. No. 4,615,876) or such ligands incorporating amide donors (WO 94/08949); the tetradentate ligands of WO 94/22816; diaminedithiols, tetraamines or dithiosemicarbazones. Stable technetium complexes are also formed with macrocyclic amine or amide ligands such as cyclam, oxocyclam (which forms a neutral technetium complex) or dioxocyclam. Suitable ligands for indium, yttrium and gadolinium are described in Sandoz WO 91/01144, preferred are macrocyclic aminocarboxylate and aminophosphonic acid ligands. Non-ionic (i.e. neutral) metal complexes of gadolinium are known and examples are described in U.S. Pat. No. 4,885,363.

When the detectable moiety is a radioactive isotope of iodine the radioiodine atom is preferably attached via a direct covalent bond to an aromatic ring such as a benzene ring, or a vinyl group since it is known that iodine atoms bound to saturated aliphatic systems are prone to in vivo metabolism and hence loss of the detectable moiety.

The compounds of the present invention may be prepared as follows:

When the detectable moiety is radioactive iodine, the R¹⁻⁵ group is chosen to include either a non-radioactive halogen atom (to permit radioiodine exchange), an activated aryl ring (e.g. a phenol group) or an organometallic precursor compound such as a trialkyltin, trialkylsilyl or other such moiety known to those skilled in the art. Examples of suitable R¹⁻⁵ groups to which radioactive iodine can be attached are given below:

Both contain substituents which permit facile radioiodine substitution onto the aromatic ring. Alternative substituents containing radioactive iodine can be synthesised by direct iodination via radiohalogen

When the detectable moiety is a radioactive or paramagnetic metal ion the metal is preferably attached as a metal complex, i.e. a chelating agent is attached to the synthetic HLE inhibitor giving a chelate-HLE inhibitor conjugate. Such chelate-HLE inhibitor conjugates can be prepared using the bifunctional chelate approach. Thus it is well known to prepare chelating agents which have attached thereto a functional group (“bifunctional chelates”). Functional groups which have been attached to chelating agents include: amine, thiocyanate, maleimide and active ester such as N-hydroxysuccinimide. Such bifunctional chelates can be reacted with suitable functional groups on the HLE inhibitor to form the desired conjugate. Examples of chelate-amine conjugates for diaminedioxime ligands are given in WO 95119187. In the particular case of β-lactams, a chelating agent can be attached at the R₁ position as follows. First a chelate-amine conjugate is converted to a chelate-isocyanate conjugate using phosgene, trichloromethylchloroformate or similar. The chelating agent may optionally be protected with protecting groups known to those skilled in the art. The resulting chelate-NCO (isocyanate) conjugate can then be reacted with the amine NH of an azetidinone ring secondary amine giving a chelating agent attached at R₁ via a urea linkage. Similarly, a chelate-amine conjugate can be converted to a chelating agent with a pendant isothiocyanate group (as e.g. described in U.S. Pat. No. 5006643 or WO 91/01144) and then reacted with an azetidinone to give a chelating agent-azetidinone conjugate linked via a thiourea bond. Alternatively, reaction of a chelate-active ester conjugate with the amine NH of an azetidinone ring would give a chelate-azetidinone conjugate linked via an amide bond. A further approach to an amide-linked conjugate would be to couple the amine group of an chelate-amine conjugate to the pendant carboxyl group of a carboxyl-functionalised azetidinone. Persons skilled in the art will recognise that many alternative syntheses of chelate-HLE inhibitor conjugates are possible based on this disclosure.

The present invention also relates to kits for the preparation of synthetic HLE inhibitors labelled with a detectable moiety. The kits are designed to give sterile products suitable for human administration, e.g. via injection into the bloodstream. Possible embodiments are discussed below. When the detectable moiety is ^(99m)Tc, the kit would comprise a vial containing the chelate-HLE inhibitor conjugate together with a pharmaceutically acceptable reducing agent such as sodium dithionite, sodium bisulphite, ascorbic acid, formamidine sulphonic acid, stannous ion, Fe(II) or Cu(I), preferably a stannous salt such as stannous chloride or stannous tartrate. Alternatively, the chelating agent-HLE inhibitor conjugate could be present as a metal complex which, upon addition of the radiometal, undergoes transmetallation (i.e. ligand exchange) giving the desired product. The kit is preferably lyophilised and is designed to be reconstituted with sterile ^(99m)Tc-pertechnetate (TcO₄ ⁻) from a ^(99m)Tc radioisotope generator to give a solution suitable for human administration without further manipulation.

The agents of the present invention may also be provided in a unit dose form ready for human injection and could for example be supplied in a pre-filled sterile syringe. When the detectable moiety is a radioactive isotope such as ^(99m)Tc, the syringe containing the unit dose would also be supplied within a syringe shield (to protect the operator from potential radioactive dose).

The above kits or pre-filled syringes may optionally contain further ingredients such as buffers; pharmaceutically acceptable solubilisers (e.g. cyclodextrins or surfactants such as Pluronic, Tween or phospholipids); pharmaceutically acceptable stabilisers/antioxidants (such as ascorbic acid, gentisic acid or para-aminobenzoic acid) or bulking agents for lyophilisation (such as sodium chloride or mannitol).

The structures of particular compounds 1-52 are set out below. Preparation of these compounds is described in Examples 1 to 12. NMR data for the compounds is given in Tables 1 to 19. Biological properties of compounds 4, 4a, 4b, 16, 17, 24, 28, 38, 42, 48, 49, 51 and 52 are shown in Examples 13 to 17 and in Tables 20 to 25.

COMPOUND STRUCTURES

Compound number R₁ R₂ 2 Ot-Bu I 3 OH I 4 4-methyl-piperazinyl I 5 4-methyl-piperazinyl Sn(n-Bu)₃

Compound number R₃ R₄ n 1 I NCO 1 6 OH NHBOC 2 7 OBn NHBOC 2 8 OBn NH₂ 2 9 OBn NCO 2

Compound number R₅ 10 TsO 11 Ph₃CS

Compound number R₆ 12 SCH₂CH₂OCH₃

Compound number X R₇ R₈ R₉ 13 S OBn H H 14 SO₂ OBn H H 15 SO₂ OH H H 16 SO₂ OH I H 17 SO₂ OH I I

Compound number R₁₀ 18 COOH 19 CNO

Compound number R₁₁ R₁₂ 20 Ot-Bu Br 21 OH Br 22 4-methylpiperazinyl Br 23 4-methylpiperazinyl Sn(n-Bu)₃ 24 4-methyipiperazinyl I

Compound 25

Compound number R₁₃ 26 Br 27 Sn(n-Bu)₃ 28 I

Compound number R₁₄ R₁₅ 29 COOH NHCO₂t-Bu 30 CO₂CH₂Ar NHCO₂t-Bu 31 CO₂CH₂Ar NH₃ ⁺Cl⁻ 35 CO₂CH₂Ar NCO

Compound number R₁₆ 32 OCH₂Ar 33 OH

Compound 34

Compound number R₁₇ 36 OCH₂Ar 37 OH 38 Ligand 1

Compound 39

Compound number R₁₈ 40 OCH₂Ar 41 OH 42 Ligand 1 51 Ligand 2

Compound number R₁₉ 43 NHCO₂t-Bu 44 NH₃ ⁺ 45 NCO

Compound number R₂₀ 46 OCH₂Ar 47 OH 48 Ligand 1

Compound number R₂₁ 49 Ligand 1

52 Ligand 2

Compound 50

In one aspect of the present invention, the desired agent is required to label human granulocytes selectively in whole blood (either in vitro or in vivo). In normal human blood erythrocytes outnumber granulocytes by a factor of at least 1000:1 but erythrocytes do not accumulate at sites of infection/inflammation hence the labelled compound must exhibit high selectivity for granulocytes. Studies on the in vitro human blood cell uptake of ¹²³I-labelled and ^(99m)Tc-labelled β-lactam HLE inhibitors have demonstrated selective uptake in human granulocytes (see Example 14 and Table 23). Table 23 shows that compounds 4, 4a, 4b, 16, 17, 24, 28, 38, 42, 48, 49, 51 and 52 all show some degree of selectivity for granulocytes over a mixture of monocytes/lymphocytes when approximately equivalent numbers of monocytes/lymphocytes and granulocytes are present. Since human granulocytes contain significant levels of HLE whereas erythrocytes (red blood cells), monocytes and lymphocytes (subsets of the leucocyte cell population) contain essentially no HLE, this selectivity is a strong indication that affinity for HLE is involved. Furthermore, Table 23 shows that there is a correlation between the in vitro potency (measured for the non-radioactive iodine-labelled compounds and for the unlabelled chelate conjugates, compounds 38, 42, 48, 49, 51 and 52) and selectivity for granulocytes. The implication is that retention within the granulocyte is due to binding to intracellular elastase. Preferred synthetic HLE inhibitors of the present invention are therefore those with an in vitro potency (k_(inact)/K_(i)) of greater than 10,000 M/sec.

Whole blood also contains plasma proteins which are capable of binding to a wide range of substances and hence may compete effectively for the compound once it is introduced into the blood. Hence the preferred agent should also exhibit low plasma protein binding (PPB). Preferred compounds have a PPB of less than 95%. Most preferred have a PPB of less than 60%. Since lipophilic compounds are particularly susceptible to non-specific plasma protein binding, preferred compounds have an octanol/water partition coefficient (LogP) of ≦2. When intracellular HLE is the target and consequently the agent must be capable of crossing cell membranes, compounds with a minimum octanol/water partition coefficient (P) of 0.3 are preferred. Table 23 shows that, in human whole blood, compounds 4, 16 and 24 exhibit equivalent uptake in granulocytes and erythrocytes. This implies a selectivity factor for granulocytes over erythrocytes of at least 1000:1 and shows that the compounds of the present invention are capable of successfully labelling granulocytes in human whole blood despite the competition from excess erythrocytes and plasma proteins. It is believed that the superior granulocyte selectivity of compound 4 may be due to a combination of HLE potency and reduced non-specific binding to red blood cells or plasma proteins. It is postulated that the amine substituent facilitates selective retention in granulocytes due to diffusion of the uncharged inhibitor into the cell and its subsequent trapping via protonation of the basic piperazine amine within the more acidic milieu of the azurophil granule of the granulocyte. The protonated inhibitor cannot readily diffuse back across the granulocyte membrane. Such more acidic environments are not present within erythrocytes, monocytes or lymphocytes.

By virtue of the single substituent at the 4 position of the azetidinone ring, compound 4 has a chiral centre. The enantiomers were resolved (Example 1, step F) and one (4a) was found to exhibit markedly superior in vitro potency and granulocyte selectivity (Table 23) compared to the other (4b). Thus efficacy is highly sensitive to stereochemical effects, i.e. chirality. Therefore chiral compounds are also encompassed by the present invention.

Further improvements in potency have been achieved by the introduction of alkyl substituents at the homochiral benzylic R₁ position, demonstrated by compounds 24 and 28, since these are known to give more potent HLE inhibitors (EP 0595557 A1) e.g.:

The radiolabelled β-lactam HLE inhibitors of the present invention have also been studied in vivo in a rat model of inflammation/infection. The results on such studies are given in Table 24. The known inflammation/infection agent ^(99m)Tc-HMPAO ex-vivo labelled human leucocytes was shown to locate at the site of infection in the model used. ^(99m)Tc-red blood cells was used as the negative control agent comparison. It can be seen that ¹²³I-labelled compounds 4/4a show significantly better uptake in the infected region than the ^(99m)Tc-rbc control, and have characteristics which more closely resemble the proven infection agent ^(99m)Tc-wbc. When ¹²³I-compound 4 is used to label human leucocytes ex-vivo the infected/normal ratio is higher than that obtained by direct injection. It is believed that the target to background ratios obtained in the rat model of infection/inflammation almost certainly underestimate the human situation because the potency of similar β-lactam inhibitors for rat elastase is known to be up to 2 orders of magnitude less than that for human leucocyte elastase.

Experiments with human plasma clots in vitro have been performed as described in Example 17. In clots enriched with granulocytes to a final concentration of 10⁶/ml there was an approximate 7-9 fold increase in the uptake of a potent elastase inhibitor compared to those clots formed without added cells. This observation indicates the potential for radiolabelled β-lactam HLE inhibitors to be specifically taken up in thrombi and other lesions where granulocyte accumulation is active.

Table 25 compares the thyroid uptake of the radioiodine compounds of the present invention with that of free ¹²³I-iodide ion. The lack of thyroid uptake is evidence that the compounds do not undergo in vivo metabolic de-iodination. There was no evidence either for the release of pertechnetate in animals dosed with ^(99m)Tc-labelled HLE inhibitors. This implies that the technetium is not released from the chelate conjugate in vivo.

Abbreviations HLE = human leucocyte elastase PPB = plasma protein binding rbc = red blood cell wbc = white blood cell ACD = acid citrate dextrose HBSS = Hanks balanced salt solution RCP = radiochemical purity Me = methyl Et = ethyl ^(t-)Bu = tertiary-butyl Ph = phenyl Bn = benzyl Ac = acetyl Ts = tosyl, i.e. para-toluenesulphonyl Ar = aryl DMF = N,N-dimethyl formamide DMSO = dimethyl sulphoxide THF = tetrahydrofuran LDA = lithium diisopropylamide PAA = peracetic acid TFA = trifluoroacetic acid BOC = tertiary-butoxycarbonyl HBTU = O-(1H-benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate DMAP = 4-(N,N-dimethylamino)pyridine MCPBA = meta-chloroperbenzoic acid

EXPERIMENTAL EXAMPLE 1 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxyl-1-[(4-iodo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (compound 4)

Step A 4-Lodobenzylisocyanate (Compound 1)

To a solution of triphosgene (1.27 g, 4.28 mmol) in refluxing ethyl acetate (20 ml) under nitrogen was added dropwise, over 2 hours, a solution of 4-iodobenzylamine (1.0 g, 4.29 mmol) in dichloromethane (40 ml). The reaction mixture was heated at reflux for a further 3 hours, filtered whilst hot and the filtrate concentrated in vacuo to give the title compound (1.10 g, 99%) as a yellow oil.

Step B 4-[4-[(1,1-Dimethylethoxy)carbonyl]phenoxy]-1-[(4-iodo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 2)

According to the method of Shrenik et al (J. Med. Chem., 35, 3745-3754 (1992)), 4-iodobenzylisocyanate (1.10 g, 4.25 mmol) and 4-[4-[(1,1-dimethylethoxy)carbonyl]phenoxy-3,3-diethyl-2-azetidinone (J. Med. Chem., 35, 3745-3754 (1992)) (0.62 g, 1.96 mmol) gave, following purification by flash column chromatography (gradient from petrol to EtOAc/petrol, 1:3), the title compound (0.72 g, 64%) as a solid.

Step C 4-[(4-Carboxy)phenoxy]-3,3-diethyl-1-[(4-iodo)benzylaminocarbonyl]-2-azetidinone (Compound 3)

According to the method of Shrenik et al (J. Med. Chem., 35, 3745-3754 (1992)), 4-[4-[(1,1-dimethylethoxy)carbonyl]phenoxy]-1-[(4-iodo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (0.72 g, 1.2 mmol) gave, following recrystallisation (Et₂O/EtOAc), the title compound (0.44 g, 68%) as a solid.

Step D 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(4-iodo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 4)

According to the method of Doherty et al (EP 0 595 557 A1), 4-[(4-carboxy)phenoxy]-3,3-diethyl-1-[(4-iodo)benzylaminocarbonyl]-2-azetidinone (0.44 g, 0.84 mmol) gave, following purification by flash column chromatography (gradient from EtOAc to MeOH/EtOAc, 1:4), the title compound (0.31 g, 79%) as a yellow oil.

Step E 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[[4-tri-(n-butyl)stannyl]benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 5)

4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(4-iodo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (0.02 g, 0.033 mmol) was dissolved in dry toluene (5 ml) under argon and heated to reflux. A catalytic amount of Pd(PPh₃)₄ (20 mg) and bis(tributyl)tin (100 ml, 0.198 mmol) were added and the resulting mixture heated at reflux for 5.5 hours. The reaction mixture was cooled to room temperature and filtered through a celite pad. The filtrate was concentrated in vacuo and the product purified by flash column chromatography (MeOH/Et₃N/EtOAc, 10:1:89) to give the title compound (5 mg, 20%).

Step F Resolution of the enantiomers of 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(4-iodo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 4)

Compound 4 was separated into its two enantiomers, 4a and 4b, by chiral HPLC using HPLC system G, example 12 yielding isomer 4a from the fraction collected between 14 and 15 minutes and isomer 4b between 18 and 19 minutes. The solvents were removed in vacuo and each product extracted from the resulting residue into dichloromethane (4×20 ml), dried (MgSO₄) and concentrated in vacuo to give each enantiomer as a solid. Both products were reanalysed by chiral HPLC. The enantiomeric purities were shown to be greater than 75%.

Step G Synthesis of ¹²³I-labelled 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(4-iodo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 4) (Racemate)

4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[[4-tri-(n-butyl)stannyl]benzylaminocarbonyl]-3,3-diethyl-2-azetidinone in MeOH (50 μg, 0.6×10⁻⁷ mol, 50 μl) was added to ammonium acetate buffer (pH 4, 0.2 M, 200 μl) in a 1 ml Eppendorf vial, followed by aqueous Na¹²⁷I in 0.01 M NaOH (7.5 μg, 0.5×10⁻⁷ mol, 10 μl) and Na¹²³I (50 μl, carrier free, 50-100 MBq). The solution was thoroughly mixed and PM (0.01 M, ca. 1×10⁻⁷ mole, 10 μl) added. The solution was again thoroughly mixed and incubated at ambient laboratory temperature for at least 5 minutes and the desired product HPLC purified using system B, example 12. The organic eluent component in the purified sample was removed and the sample diluted with sodium phosphate buffer (pH 7.4, volume variable) to ensure the purified compound was present in a biologically acceptable medium for testing. The radiochemical purity of the purified compound 4 (racemate) was measured using HPLC system B, example 12 before and after in vitro or in vivo testing. Results of RCP measurement are presented in Table 20. The identity of the ¹²³I species was confirmed by HPLC co-elution with the chemically characterised ¹²⁷I analogue (Example 1, step D). The retention times of the ¹²³I and ¹²⁷I species are presented in Table 21.

Step H Synthesis of ¹²³I Labelled Compounds 4a and 4b

A sample of ¹²³I-compound 4 racemate was synthesised and purified according to the HPLC method detailed in system C, example 12. This was to ensure that the pH of the purified racemic compound was compatible with the HPLC column material used for purification of optical isomers (below). The organic HPLC eluent was removed in vacuo at ambient laboratory temperature and the sample then diluted with sodium phosphate buffer (pH 6.0) to make the total volume ca 1 ml. The racemate was purified into the two optical isomers using the HPLC system D, example 12. The two enantiomers, 4a and 4b, were collected and the is HPLC organic eluent removed in vacuo and the radiochemical (chiral) purity measured after testing using HPLC system D, Example 12. Results of RCP testing are presented in Table 20.

Example 2 4-[2-Methoxyethylsulfonyl]-1-[(4-hydroxy) (3-iodo)phenylethylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 16) and 4-[2-Methoxyethylsulfonyl]-1-[(3,5-diiodo) (4-hydroxy)phenylethylaminocarbonyl]-3.3-diethyl-2-azetidinone (Compound 17)

Step A N-t-Butoxycarbonyl (4-Hydroxy)-2-phenylethylamine (Compound 6)

Tyramine (0.20 g, 1.46 mmol) was dissolved in methanol (5 ml) at room temperature under nitrogen. A solution of di-tert-butyldicarbonate (0.318 g, 1.46 mmol) in methanol (1 ml) was added followed by triethylamine (200 ml, 1.46 mmol). The reaction mixture was stirred for 4.5 hours and the solvent then removed in vacuo. The residue was partitioned between ethyl acetate and water. The organic layer was separated, dried (Na₂SO₄) and concentrated in vacuo to give the crude product. Purification by flash column chromatography (petrol/EtOAc, 1:1) gave the title compound (0.34 g, 98%) as a yellow oil.

Step B N-t-Butoxycarbonyl (4-Benzyloxy)-2-phenylethylamine (Compound 7)

Sodium hydride (0.046 g, 1.14 mmol) was suspended in dry THF (5 ml) at room temperature under nitrogen. A solution of N-t-butoxycarbonyl (4-hydroxy)-2-phenylethylamine (0.27 g, 1.14 mmol) in dry THF (5 ml) was added dropwise to the reaction mixture over 20 minutes. Benzyl bromide (135 μl, 1.14 mmol) was added as a single aliquot and the resulting mixture stirred for 24 hours. The reaction was quenched by pouring into water (50 ml) and the aqueous layer extracted with diethyl ether (3×20 ml). The combined organic extracts were dried (MgSO₄) and concentrated in vacuo. The crude product was purified by flash column chromatography (petrol/Et₂O, 8:1) to give the title compound (0.217 g, 58%) as a solid.

Step C (4-Benzyloxy)-2-phenylethylamine hydrochloride salt (Compound 8)

N-t-Butoxycarbonyl (4-benzyloxy)-2-phenylethylamine (0.199 g, 0.608 mmol) was dissolved in a 3 M solution of hydrochloric acid in ethyl acetate (10 ml) and the mixture stirred for 1 hour at room temperature. The precipitate was isolated by filtration to give a white solid (0.056 g) and the filtrate concentrated in vacuo to obtain a pale yellow solid (0.079 g). Both products were combined to give a total sample of the title compound (0. 135 g, 84%) as a pale yellow solid.

Step D (4-Benzyloxy)-2-phenylethylisocyanate (Compound 9)

(4-Benzyloxy)-2-phenylethyiamine hydrochloride salt (1.413 g, 5.35 mmol) was taken up in ethyl acetate (15 ml) and 2M aqueous sodium hydroxide (3 ml) and the resulting mixture stirred at room temperature for 1 hour. The aqueous layer was separated and extracted with dichloromethane (3×20 ml). The organic extracts were combined and concentrated in vacuo to obtain the free amine (1.32 g, 97%). According to the procedure given in example 1, step A, a portion of this amine (0.19 g, 0.84 mmol) gave the title compound (0.187 g, 88%) as a solid.

Step E Ethylene Glycol Methyl Ether Tosylate (Compound 10)

To tosyl chloride (50.0 g, 0.263 mol) at 0° C. and under nitrogen were added anhydrous dichloromethane (80 ml), anhydrous pyridine (23 ml, 24.3 g, 0.29 mol), 2-methoxyethanol (21.0 ml, 20.0 g, 0.263 mol) and a catalytic quantity of DMAP. After 10 minutes the mixture was warmed to room temperature, at which it was stirred for 16 hours. Dichloromethane (100 ml) and 1 M aqueous hydrochloric acid (50 ml) were added. The organic layer was isolated and washed with 1 M aqueous hydrochloric acid (4×30 ml) and water (4×30 ml), dried (Na₂SO₄) and concentrated in vacuo to give the title compound (51.68 g, 85%) as an oil.

Step F S-Triphenylmethyl 2-Methoxyethanethiol (Compound 11)

To sodium hydride (2.17 g, 0.09 mol) under nitrogen was added anhydrous THF (50 ml). The mixture was cooled to 0° C. and triphenylmethylmercaptan (24.88 g, 0.09 mol) in anhydrous THF (50 ml) added dropwise over 15 minutes. After a further 10 minutes at 0° C. the mixture was warmed to room temperature, at which it was stirred for 1 hour. The mixture was then recooled to 0° C. and ethylene glycol methyl ether tosylate (20.72 g, 0.09 mol) in dry THF (50 ml) added dropwise over 15 minutes. After warming to room temperature the mixture was left to stir for 16 hours. The mixture was filtered and the precipitate washed with dichloromethane. The combined filtrates were concentrated in vacuo. The residue was dissolved in dichloromethane, washed with water (3×50 ml), dried (Na₂SO₄) and concentrated in vacuo. Purification by flash column chromatography (gradient from 100% petrol to 100% EtOAc) and recrystallisation (petrol) gave the title compound (12.39 g, 41%) as a pale brown solid.

Step G 4-[2-Methoxyethylthio]-3,3-diethyl-2-azetidinone (Compound 12)

To S-triphenylmethyl 2-methoxyethanethiol (1.37 g, 4.1 mmol) in dichloromethane (30 ml) under nitrogen were added triethylsilane (0.953 g, 1.31 ml, 8.2 mmol) and trifluoroacetic acid (0.632 ml, 0.935 g, 8.2 mmol). The mixture was stirred at room temperature for 16 hours. Acetone (50 ml) was added and the mixture neutralised with 2 M aqueous sodium hydroxide. 1 M Aqueous sodium hydroxide (24 ml, 24 mmol), 4-acetoxy-3,3-diethyl-2-azetidinone (J. Med. Chem., 35, 3745-3754 (1992)) (0.690 g, 6.00 mmol) and acetone (10 ml) were then added and the mixture stirred at room temperature for 23 hours. The solvents were removed in vacuo and to the residue were added water (50 ml) and dichloromethane (50 ml). The organic layer was isolated and the water layer extracted further with dichloromethane (3×30 ml). The 4 organic layers were combined and washed with water (30 ml) and saturated brine (30 ml), dried (Na₂SO₄) and concentrated in vacuo. Purification by flash column chromatography (gradient from petrol/EtOAc, 9:1 to EtOAc) gave the title compound (0.51 g, 63%) as an oil.

Step H 4-[2-Methoxyethylthio]-1-[(4-benzyloxy)phenylethylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 13)

According to the method of Shrenik et al (J. Med. Chem., 35, 3745-3754 (1992)) 4-[2-methoxyethylthio]-3,3-diethyl-2-azetidinone (550 mg, 2.53 mmol) and (4-benzyloxy)-2-phenylethylisocyanate, prepared as in example 2, step D, (1.366 g, 5.39 mmol) gave, following purification by flash column chromatography (EtOAc/petrol, 7:3), the title compound (391 mg, 33%) as an oil.

Step I 4-[2-Methoxyethylsulfonyl]-1-(4-benzyloxy)phenylethylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 14)

To 4-[2-methoxyethylthio]-1-[(4-benzyloxy)phenylethylaminocarbonyl]-3,3-diethyl-2-azetidinone (358 mg, 0.76 mmol) in dichloromethane (10 ml) was added excess metachloroperoxybenzoic acid (MCPBA) (approximately 50% pure, 525 mg) and the mixture stirred at room temperature for 16 hours. The mixture was poured into an aqueous solution containing 8% (w/v) sodium bicarbonate and 8% (w/v) sodium sulphite (50 ml) and stirred vigorously at room temperature for 30 minutes. The organic layer was isolated and washed with saturated brine (5 ml) and water (5 ml). The aqueous layer was extracted with dichloromethane (20 ml). The organic layers were combined, dried (Na₂SO₄) and concentrated in vacuo. Purification by flash column chromatography (petrol/EtOAc, 7:3) gave the title compound (314 mg, 82%) as an oil.

Step J 4-[2-Methoxyethylsulfonyl]-1-(4-hydroxy)phenylethylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 15)

Cyclohexene (400 μl, 3.95 mmol) was added to a solution of 4-[2-methoxyethylsulfonyl]-1-[4-benzyloxy)phenylethylaminocarbonyl]-3,3-diethyl-2-azetidinone (195 mg, 0.39 mmol) in dry ethanol (7 ml) at room temperature under argon. 10% Palladium on charcoal (202 mg) was added and the reaction mixture heated at reflux for 4 hours. The reaction mixture was then allowed to cool to room temperature, filtered through a pad of celite, washing with ethanol (15 ml), and the filtrate concentrated in vacuo. The crude product was purified by flash column chromatography (petrol/EtOAc, 1:1) to give the title compound (127 mg, 79%) as an oil.

Step K 4-[2-Methoxyethylsulfonyl]-1-[(4-hydroxy)(3-iodo)phenylethylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 16)

To 4-[2-methoxyethylsulfonyl]-1-[(4-hydroxy)phenylethylaminocarbonyl]-3,3-diethyl-2-azetidinone (52 mg, 1.3×10⁻⁴ mol) dissolved in MeOH (10 ml) was added Nal (19 mg, 1.3×10⁻⁴ mol), and aqueous PAA (0.1 M, 1.3×10⁻⁴ mol, 1.27 ml). The solution was stirred at ambient laboratory temperature and further mole equivalents of PAA were added at approximately 1 and 2 hours after the addition of the first aliquot of PAA. The dissolved product was HPLC purified using system E, Example 12. The purified HPLC fractions were concentrated in vacuo to give the title compound (21 mg, 30%).

Step L 4-(2-Methoxyethylsulfonyl)-1-[(3,5-diiodo)(4-hydroxy)phenylethylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 17)

To 4-[2-methoxyethylsulfonyl]-1-[(4-hydroxy)phenylethylaminocarbonyl]-3,3-diethyl-2-azetidinone (13 mg, 3.1×10⁻⁵ mol) was added Nal (5 mg, 3.1×10⁻⁵ mol) and aqueous PAA (0.3 ml, 0.1 M, 3.1×10⁻⁵ mol). The solution became orange/brown immediately on addition of peracetic acid and was stirred at ambient laboratory temperature. Further aliquots of Nal (3.1×10⁻⁵ mol) and PAA (0.3 ml, 3.1×10⁻⁵ mol) were added at approximately 2½ hours and 4 hours post reaction initiation. The dissolved product was HPLC purified using system E, Example 12. The purified fractions were concentrated in vacuo to give the title compound (4.4 mg, 21%).

Step M Synthesis of ¹²³I-labelled 4-[2-Methoxyethylsulfonyl]-1-[(4-hydroxy)(3-iodo)phenylethylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 16)

4-[2-Methoxyethylsulfonyl]-1-[(4-hydroxy)phenylethylaminocarbonyl]-3,3-diethyl-2-azetidinone in MeOH (50 μg, 1×10⁻⁷mol, 50 μl) was iodinated according to the procedure described in Example 1, step G. The product was purified by HPLC using system A, Example 12 and diluted with sodium phosphate buffer (pH 7.4) in an identical manner to that detailed in Example 1, step G. RCP measurements are detailed in Table 20. The identity of the ¹²³I species was confirmed by HPLC co-elution with the chemical characterised ¹²⁷I analogue (Example 2, step K). The retention times of the ¹²³I and ¹²⁷I species are presented in Table 21.

Step N Synthesis of ¹²³I-labelled 4-(2-Methoxyethylsulfonyl)-1-[(3,5-diiodo)(4-hydroxy)phenylethylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 17)

The synthesis of the title compound was identical to the method used in example 1, step G. This method produces a mixture (roughly 50:50) of mono-iodo and di-iodo species. The desired product was purified by HPLC using system A, Example 12, the organic eluent removed and the sample diluted with aqueous sodium phosphate buffer prior to testing as detailed in example 1, step G. The radiochemical purity of the purified compound was measured before and after screening using HPLC system A, Example 12. Results of RCP measurement are detailed in Table 20. The identity of the ¹²³I-species was confirmed by HPLC coelution with the chemically characterised ¹²⁷I analogue (Example 2, step L). The retention times of the ¹²³I and ¹²⁷I species are presented in Table 21.

Example 3 4S-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(R-α-n-propyl)-(4-iodo)benzyiaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 24)

Step A R-α-n-Propyl-(4-bromo)phenylacetic Acid (Compound 18)

According to the method of Finke et al (UK Patent Application GB 2 280 673 A), 4-bromophenylacetic acid (17.24 g, 0.08 mol) and 1-bromopropane (14.5 ml, 0.16 mol) gave, following purification by flash column chromatography (gradient petrol/acetic acid, 99:1 to petrol/EtOAc/acetic acid, 64:33:1), α-n-propyl-(4-bromo)phenylacetic acid (15.49 g, 75%). To the racemic acid was added R-(+)-α-methylbenzylamine and the resulting salt recrystallised three times from ethyl acetate. The salt was taken up in 2M aqueous HCl (100 ml) and extracted into dichloromethane (100 ml). The organic layer was dried (Na₂SO₄) and concentrated in vacuo to give the title compound (3.72 g) as an oil.

Step B R-α-n-Propyl-(4-bromo)phenylmethylisocyanate (Compound 19)

According to the method of Finke et al (UK Patent Application GB 2 280 673), R-α-n-propyl-(4-bromo)phenylacetic acid (2.00 g, 7.78 mmol) gave the title compound (1.90 g, 96%) as an oil.

Step C 4S-[4-[(1,1-Dimethylethoxy)carbonyl]phenoxy]-1-[(R-α-n-propyl)-(4-bromo)benzylaminocarbonyl]-3, 3-diethyl-2-azetidinone (Compound 20)

According to the method of Shrenik et al (J. Med. Chem., 35, 3745-3754 (1992)), R-α-n-propyl-(4-bromo)phenylmethyl isocyanate (1.9 g, 7.48 mmol) and 4-[4-[(1,1-dimethylethoxy)carbonyl]phenoxy]-3,3-diethyl-2-azetidinone (J. Med. Chem., 35, 3745-3754 (1992)) (1.28 g, 4.0 mmol) gave, following purification by flash column chromatography (gradient from 100% petrol to petrol/EtOAc, 1:1), the title compound (0.73 g, 32%) as an oil.

Step D 4S-[(4-Carboxy)phenoxy]-1-[(R-α-n-propyl)-(4-bromo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 21)

According to the method of Shrenik et al (J. Med. Chem., 35, 3745-3754 (1992)), 4S-[4-[(1,1-dimethylethoxy)carbonyl]phenoxy]-1-[(R-α-n-propyl)-(4-bromo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (0.73 g, 1.27 mmol) gave the title compound (0.66 g, 100%) as a solid.

Step E 4S-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(R-α-n-propyl)-(4-bromo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 22)

According to the method of Doherty et al (EP 0 595 557 A1), 4S-[(4-carboxy)phenoxy]-1-[(R-α-n-propyl)-(4-bromo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (0.66 g, 1.27 mmol) gave, following purification by flash column chromatography (gradient from hexane to EtOAc/hexane, 1:1 to MeOH/EtOAc, 1:9) and recrystallisation (diethyl ether/petrol), the title compound (0.37 g, 60%) as white crystals.

Step F 4S-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(R-α-n-propyl]-[4-[tri-(n-butyl)-stannyl]benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 23)

According to the procedure described in Example 1, step E, 4S-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(R-α-n-propyl)-(4-bromo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (80 mg, 0.13 mmol) gave, following purification by HPLC using system J, Example 12, the title compound (15.5 mg, 15%) as an oil.

Step G Synthesis of ¹²³I-labelled 4S-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(R-α-n-propyl)-(4-iodo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 24)

According to the procedure described in Example 1, step G, 4S-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(R-α-n-propyl)-[4-[tri-(n-butyl)-stannyl]benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (50 μg, 6.18×10⁻⁸ mol) gave the title compound.

Example 4 4S-(Pyridyl-3-oxy)-1-[(R-α-n-propyl)-(4-iodo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 28)

Step A 4-(Pyridyl-3-oxy)-3,3-diethyl-2-azetidinone (Compound 25)

According to the method of Shrenik et al (J. Med. Chem., 35, 3745-3754 (1992), 3-hydroxypyridine (0.598 g, 6.291 mol) and 4-acetoxy-3,3-diethyl-2-azetidinone (J. Med. Chem., 35, 3745-3754 (1992)) (1.00 g, 5.40 mol) gave, following purification by flash column chromatography (MeOH/EtOAc, 1:4), the title compound (900 mg, 76%) as an oil.

Step B 4S-(Pyridyl-3-oxy)-1-[(R-α-n-propyl)-(4-bromo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 26)

According to the method of Shrenik et al (J. Med. Chem., 35, 3745-3754 (1992)), R-α-n-propyl-(4-bromo)phenylmethyl isocyanate, prepared as in example 3, step B (1.32 g, 5.19 mmol) and 4-(pyridyl-3-oxy)-3,3-diethyl-2-azetidinone (0.573 mg, 2.60 mmol) gave, following purification by flash column chromatography (gradient from diethyl ether/petrol, 1:1 to diethyl etherlpetrol, 7:1 to diethyl etherlpetrol, 9:1), the title compound (0.35 g, 28%) as an oil.

Step C 4S-(Pyridyl-3-oxy)-1-[(R-α-n-propyl)-[[4-tri-(n-butyl)-stannyl]benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (compound 27)

According to the procedure described in Example 1, step E, 4S-(pyridyl-3-oxy)-1-[(R-α-n-propyl)-(4-bromo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (90 mg, 0.19 mmol) gave, following purification by flash column chromatography (gradient from EtOAc/petrol, 1:4 to EtOAc/petrol, 1:1 to EtOAc/petrol, 7:3), the title compound (29 mg, 22%) as an oil.

Step D Synthesis of ¹²³I-labelled 4S-(pyrdyl-3-oxy)-1-[(R-α-n-propyl)-(4-iodo)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 28)

According to the procedure described in Example 1, step G, 4S-(pyridyl-3-oxy)-1-[(R-α-n-propyl)-[[4-tri-(n-butyl)-stannyl]benzylaminocarbonyl]-3,3-diethyl-2-azetidinone(50 μg, 7.31×10⁻⁸ mol) gave the title compound.

Example 5 Conjugate Between Chelate, 3,3,6,9,9-Pentamethyl-6-aminomethyl-4,8-diazaundecane-2,10-dionedioxime and 4-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(4-carboxy)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 38)

Step A 4-(N-Boc-aminomethyl)benzoic Acid (Compound 29)

To a solution of 4-(aminomethyl)benzoic acid (1 g, 6.62 mmol) in 4M NaOH (21 ml) at room temperature was added di-tert-butyldicarbonate (1.67 ml, 7.28 mmol) and the mixture stirred for 19 hours. The reaction was acidified to pH 2.0 with concentrated hydrochloric acid and the mixture extracted with ethyl acetate (3×50 ml). The combined organic extracts were dried (Na₂SO₄) and concentrated in vacuo to give the title compound (1.136 g, 68%) as a solid.

Step B 4-(N-Boc-aminomethyi)benzoic Acid, Benzyl Ester (Compound 30)

To a mixture of 4-(N-Boc-aminomethyl)benzoic acid (500 mg, 1.99 mmol), DMAP (catalytic amount), benzyl alcohol (226 μl, 2.19 mmol) and dichloromethane (20 ml) was added dicyclohexylcarbodiimide (1M solution in dichloromethane, 2.19 ml, 2.19 mmol) and the mixture stirred at room temperature for 60 hours. The precipitate was removed by filtration and the filtrate concentrated in vacuo. Diethyl ether (50 ml) was added to the residue, the resulting precipitate removed by filtration and the filtrate concentrated in vacuo. Purification by flash column chromatography (petrol/EtOAc, 3:1) gave the title compound (412 mg, 61%) as a solid.

Step C 4-(Aminomethyl)benzoic Acid, Benzyl Ester, Hydrochloride Salt (Compound 31)

According to the procedure described in example 2, step C, 4-(N-Boc-aminomethyl)benzoic acid, benzyl ester (398 mg, 1.17 mmol) gave the title compound (288 mg, 93%) as a solid.

Step D 4-Benzyloxy-(1-N-methylpiperazine)benzamide (Compound 32)

According to the method of Doherty et al (EP 0 595 557 A1), benzyloxybenzoic acid (15.22 g, 0.06 mol) gave the title compound (18.93 g, 99%) as a pale yellow solid.

Step E 4-Hydroxy-(1-N-methylpiperazine)benzamide (Compound 33)

According to the procedure described in Example 2, step J, 4-benzyloxy-(1-N-methylpiperazine)benzamide (4.555 g, 0.015 mol) gave, following purification by flash column chromatography (MeOH/EtOAc, 1:9), the title compound (2.41 g, 73%) as a solid.

Step F 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-3,3-diethyl-2-azetidinone (Compound 34)

According to the method of Shrenik et al (J. Med. Chem., 35, 3745-3754 (1992)), 4-hydroxy-(1-N-methylpiperazine)benzamide (2.41 g, 0.011 mol) and 4-acetoxy-3,3-diethyl-2-azetidinone (J. Med. Chem., 35, 3745-3754 (1992), 3.04 g, 0.017 mol), followed by a further addition after 60 hours of 4-acetoxy-3,3-diethyl-2-azetidinone (0.95 g, 5.31 mmol) gave, following purification by flash column chromatography (gradient from petrol/EtOAc, 1:1 to MeOH/EtOAc, 1:9 to MeOH/EtOAc, 9:1), the title compound (1.60 g, 42%) as an oil.

Step G 4-(Benzyloxycarbonyl)benzylisocyanate (Compound 35)

To 4-(aminomethyl)benzoic acid, benzyl ester, hydrochloride salt, prepared as in Example 5, step C (288 mg, 1.04 mmol) at 0° C. was added saturated aqueous NaHCO₃ (15 ml) and dichloromethane (20 ml). After 20 minutes stirring was ceased and the two layers were allowed to separate. Phosgene (20% solution in toluene, 1.1 ml, 2.18 mmol) was added rapidly to the lower layer and stirring resumed immediately. After 1 hour the organic layer was isolated. The aqueous layer was extracted with dichloromethane (3×20 ml). The four organic layers were combined, dried (Na₂SO₄) and concentrated in vacuo to give the title compound (261 mg, 94%) as an oil.

Step H 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[4-(benzyloxycarbonyl)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 36)

According to the method of Shrenik et al (J. Med. Chem., 35, 3745-3754 (1992)), 4-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-3,3-diethyl-2-azetidinone (160 mg, 0.463 mmol) and 4-(benzyloxycarbonyl)benzylisocyanate (261 mg, 0.98 mmol) gave, following purification by flash column chromatography (MeOH/EtOAc, 1:4), the title compound (171 mg, 60%) as an oil.

Step I 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(4-carboxy)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 37)

According to the procedure described in Example 2, step J, 4-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[4-(benzyloxycarbonyl)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (159 mg, 0.26 mmol) gave the title compound (107 mg, 79%) as a solid.

Step J Conjugate Between Chelate, 3,3,6,9,9-Pentamethyl-6-aminomethyl-4,8-diazaundecane-2,10-dionedioxime and 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(4-carboxy)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 38)

To 4-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(4-carboxy)benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (30 mg, 0.057 mmol), DMAP (catalytic amount) and N-hydroxysuccinimide (7 mg, 0.063 mmol) in a mixture of dichloromethane (1 ml) and acetonitrile (1 ml) was added dicyclohexylcarbodiimide (1M solution in dichloromethane, 0.63 ml, 0.063 mmol) and the mixture stirred at room temperature under nitrogen for 19 hours. A solution of 3,3,6,9,9-pentamethyl-6-aminomethyl-4,8-diazaundecane-2,10-dionedioxime (WO 95/19187, 27 mg, 0.086 mmol) in acetonitrile (1 ml) was added and the mixture stirred for a further 5 hours. The mixture was filtered, diluted with acetonitrile (1 ml) and purified by HPLC using system H, Example 12 to give the title compound (2 mg, 4%) as a solid

Example 6 Conjugate Between Chelate, 3,3,6,9,9-Pentamethyl-6-aminomethyl-4,8-diazaundecane-2,10-dionedioxime and 4-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(2-carboxy)ethylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 42)

Step A 2-(Benzyloxycarbonyl)ethylisocyanate (Compound 39)

According to the procedure described in Example 5, step G, β-alanine benzylester-p-toluene sulphonate (3 g, 8.53 mmol) gave the title compound (1.44 g, 94%) as a liquid.

Step B 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[2-(benzyloxycarbonyl)ethylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 40)

According to the method of Shrenik et al (J. Med. Chem., 35, 3745-3754 (1992)), 4-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-3,3-diethyl-2-azetidinone, prepared as in Example 5, step F, (0.68 g, 1.97 mmol) and 2-(benzyloxycarbonyl)ethylisocyanate (0.705 g, 3.94 mmol) gave, following purification by flash column chromatography (gradient from petrol/EtOAc, 1:1 to MeOH/EtOAc, 1:9 to MeOH/EtOAc, 1:1), the title compound (840 mg, 78%) as an oil.

Step C 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(2-carboxy)ethylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 41)

According to the procedure described in Example 2, step J, 4-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[2-(benzyloxycarbonyl)ethylaminocarbonyl]-3,3-diethyl-2-azetidinone (420 mg, 0.76 mmol) gave the title compound (280 mg, 80%) as a solid.

Step D Conjugate Between Chelate, 3,3,6,9,9-pentamethyl-6-aminomethyl-4,8-diazaundecane-2,10-dionedioxime and 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(2-carboxy)ethylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 42)

According to the procedure described in Example 5, step J, 4-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(2-carboxy)ethylaminocarbonyl]-3,3-diethyl-2-azetidinone (100 mg, 0.22 mmol) and 3,3,6,9,9-pentamethyl-6-aminomethyl-4,8-diazaundecane-2,10-dionedioxime (WO 95/19187, 82 mg. 0.26 mmol) gave, following purification by HPLC using system H, Example 12, the title compound (4 mg, 3%) as an oil.

Example 7 Conjugate Between Chelate, 3,3,6,9,9-pentamethyl-6-aminomethyl-4,8-diazaundecane-2,10-dionedioxime and 4-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(5-carboxy)pentylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 48)

Step A N-Boc-aminocaproic Acid, Benzyl Ester (Compound 43)

According to the procedure described in Example 5, step B, N-Boc aminocaproic acid (1.0 g, 4.32 mmol) gave, following purification by flash column chromatography (petrol/EtOAc, 4:1), the title compound (1.34 g, 96%) as a liquid.

Step B Aminocaproic Acid, Benzyl Ester (Compound 44)

To N-Boc-aminocaproic acid, benzyl ester (1.125 g, 3.50 mmol) in dichloromethane (4 ml) was added trifluoroacetic acid (8 ml) and the mixture stirred at room temperature for 10 minutes. The solvents were removed in vacuo to give the title compound (1.17 g, 100%) as an oil.

Step C 5-(Benzyloxycarbonyl)pentylisocyanate (Compound 45)

According to the procedure described in Example 5, step G, aminocaproic acid, benzyl ester (1.17 g, 3.50 mmol) gave the title compound (0.922 g, 100%) as an oil.

Step D 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1l-[5-(benzyloxycarbonyl)ethylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 46)

According to the method of Shrenik et al (J. Med. Chem., 35, 3745-3754 (1992), 4-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-3,3-diethyl-2-azetidinone, prepared as in Example 5, step F, (316 mg, 0.91 mmol) and 5-(benzyloxycarbonyl)pentylisocyanate (922 mg, 3.50 mmol) gave, following purification by flash column chromatography (MeOH/EtOAc, 1:3), the title compound (0.53 g, 98%) as a pale yellow oil.

Step E 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[5-(carboxy)pentylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 47)

According to the procedure described in Example 2, step J, 4-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[5-(benzyloxycarbonyl)ethylaminocarbonyl]-3,3-diethyl-2-azetidinone (421 mg, 0.71 mmol) gave the title compound (320 mg, 90%) as a solid.

Step F Conjugate Between Chelate, 3,3,6,9,9-pentamethyl-6-aminomethyl-4,8-diazaundecane-2,10-dionedioxime and 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(5-carboxy)pentylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 48)

According to the procedure described in Example 5, step J, 4-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[5-(carboxy)pentylaminocarbonyl]-3,3-diethyl-2-azetidinone (98 mg, 0.20 mmol) and 3,3,6,9,9-pentamethyl-6-aminomethyl-4,8-diazaundecane-2,10-dionedioxime (WO 95/19187, 76 mg, 0.24 mmol) gave, following purification by HPLC using system H, Example 12, the title compound (19.7 mg, 12%) as an oil.

Example 8 Conjugate Between Chelate, 3,3,6,9,9-Pentamethyl-6-aminomethyl-4,8-diazaundecane-2,10-dionedioxime and 4-[(4-Carboxy)phenoxy]-1-[benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 49)

Step A Conjugate Between Chelate, 3,3,6,9,9-pentamethyl-6-aminomethyl-4,8-diazaundecane-2,10-dionedioxime and 4-[(4-carboxy)phenoxy]-1-[benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 49)

According to the procedure described in Example 5, step J, 4-[(4-carboxy)phenoxy]-1-[benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (J. Med. Chem., 35, 3745-3754 (1992), 100 mg, 0.25 mmol) and 3,3,6,9,9-pentamethyl-6-aminomethyl-4,8-diazaundecane-2,10-dionedioxime (WO 95/19187, 95 mg, 0.30 mmol) gave, following purification by HPLC using system H, Example 12, the title compound (18 mg, 10%) as an oil.

Example 9 Conjugate Between Chelate, 3,3,11,11-Tetramethyl-7-aminomethyl-4,7,10-triazatridecane-2,12-dionedioxime and 4-[4-[[(4-Methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(2-carboxy)ethylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 51)

Step A 3,3,11,11-Tetramethyl-7-aminomethyl-4,7,10-triazatridecane-2,12-dionedioxime (Compound 50)

To tris (2-aminoethyl)amine (4 ml, 0.027 mol), acetonitrile (70 ml) and NaHCO₃ (7.4 g, 0.088 mol) was added 3-chloro-3-methyl-2-nitroso-butane (European Patent Application 0 179 608 A2, 2.5 g, 0.019 mol) in acetonitrile (50 ml) dropwise over 20 minutes. The mixture was stirred at room temperature for 20 hours, filtered and concentrated in vacuo. The crude product was purified by HPLC using system 1, Example 12 to give the title compound (700 mg, 8%) as an oil.

Step B Conjugate Between Chelate, 3,3,11,11-Tetramethyl-7-aminomethyl-4,7,10-triazatridecane-2,12-dionedioxime and 4-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-l -[(2-carboxy)ethylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 51)

To a mixture of 4-[4-[[(4-methyl)piperazin-1-yl]carbonyl]phenoxy]-1-[(2-carboxy)ethylaminocarbonyl]-3,3-diethyl-2-azetidinone, prepared as in example 6, step C, (100 mg, 0.22 mmol), 3,3,11,11-tetramethyl-7-aminomethyl-4,7,10-triazatridecane-2,12-dionedioxime (75 mg, 0.22 mmol) and HBTU (82 mg, 0.22 mmol) under nitrogen was added anhydrous DMF (1 ml). The mixture was stirred at room temperature and diisopropylethylamine (100 μl, 1.09 mmol) added and stirring continued for 40 hours. Following dilution with MeOH/H₂O, 1:1 (4 ml) the mixture was purified by HPLC using system H, Example 12 to give the title compound (54.2 mg, 32%) as an oil.

Example 10 Conjugate Between Chelate, 3,3,11,11-Tetramethyl-7-aminomethyl-4,7,10-triazatridecane-2,12-dionedioxime and 4-[(4-Carboxy)phenoxy]-1-[benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 52)

Step A Conjugate Between Chelate, 3,3,11,11-tetramethyl-7-aminomethyl-4,7,10-triazatridecane-2,12-dionedioxime and 4-[(4-carboxy)phenoxy]-1-[benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (Compound 52)

According to the procedure described in Example 9, step B, 4-[(4-carboxy)phenoxy]-1-[benzylaminocarbonyl]-3,3-diethyl-2-azetidinone (J. Med. Chem., 35, 3745-3754 (1992), 100 mg, 0.253 mmol) and 3,3,11,11-tetramethyl-7-aminomethyl-4,7,10-triazatridecane-2,12-dionedioxime, prepared as in Example 9, step A, (87 mg, 0.253 mmol) gave, following HPLC purification using system K, Example 12, the title compound (110 mg, 60%) as a solid.

Example 11 ^(99m)Tc Labelling of Compounds 38, 42, 48, 49, 51 and 52

A solution of the compound for labelling in methanol (250 μg in 50 μl) was transferred to a N₂ filled 10 ml P6 vial followed by methanol (1 ml), deoxygenated saline (0.9% w/v, 1 ml) and aqueous sodium hydroxide (0.1 M, 18 μl). To this solution was added technetium-99m generator eluate (1 ml, approximately 0.5 GBq) and then aqueous SnCl₂ (0.1 ml, 10 μg). The labelling pH was 8.0-8.5. Vials were incubated at ambient temperature for 1 to 2 hours and the ^(99m)Tc labelled product purified by HPLC using system A, Example 12, collecting the product into a plasma coated Schott vial containing unlabelled compound (200 μg in 250 μl methanol). The organic eluant was removed in vacuo and the sample diluted with buffer as described in Example 1, step G. The radiochemical purity of the purified compounds was measured using HPLC system A, Example 12 (results are in Table 22) and the thin layer chromatography (TLC) systems described below.

TLC i) ITLC SG 2 cm×20 cm eluted with 0.9% w/v saline

ii) ITLC SG 2 cm×20 cm eluted with butan-2-one

iii) Whatman No. 12 cm×20 cm eluted with 50:50 v/v acetonitrile:H₂O

where ITLC SG=instant thin layer chromatography, silica gel impregnated sheets supplied by Gelman.

Compounds 38, 42, 48, 49, 51 and 52 remain at, or close to, the origin in TLC system (i), between the origin and the solvent front in system (ii) and close to the solvent front in system (iii).

Example 12 HPLC Details

System A

Gilson 715 control software.

Gradient T_(0′)=100%A, 0%B, T_(20′)=0%A, 100%B.

Eluent A=0.1% TFA in H₂O

Eluent B=0.1% TFA in MeCN

Flow rate=1 ml/min

Column=150×3.9 mm Waters NovaPak C-18, 4 μ packing

Detection=UV (I=220 nm); activity (g)

System B

Gilson 715 control software.

Gradient T_(0′)=60%A, 40%B, T_(20′)=0%A, 100%B.

Eluent A=0.1% TFA in H₂O

Eluent B=0.1% TFA in MeCN

Flow rate=1 ml/min

Column=150×3.9 mm Waters NovaPak C-18, 4 μ packing

Detection=UV (I=220 nm); activity (g)

System C

Gilson 715 control software.

Gradient T_(0′)=60%A, 40%B, T_(20′)=0%A, 100%B.

Eluent A=Ammonium acetate buffer (pH 4, 0.05M)

Eluent B=Acetonitrile

Flow rate=1 ml/min

Column=150×3.9 mm Waters NovaPak C-18, 4 μ packing

Detection=UV, (I=220 nm); activity (g)

System D

Gilson 715 control software.

Isocratic; Eluent 18% B, 82% A

Eluent A=Na phosphate buffer (pH 6, 0.05M)

Eluent B=Acetonitrile

Flow rate=1 ml/min

Column Chromtech Chiral AGP 150×4 mm

Detection=UV (I=220 nm); activity (g)

System E

Gilson 715 control software.

Gradient T_(0′)=100%A, 0%B, T_(20′)=0%A, 100%B.

Eluent A=H₂O

Eluent B=MeCN

Flow rate=3 ml/min

Column=300×7.8 mm Waters NovaPak C-18, 6 μm packing

Detection=UV (I=220 nm or 254 nm)

System F

Gilson 715 control software.

Gradient=T_(0′)=100% A, 0%B, T_(3′)=100% A, 0%B

T_(20′)=0%A, 100%B

Eluent A=sodium acetate buffer (pH 5.6, 50mM)

Eluent B=MeCN

Flow rate=1 ml/min

Column=150×3.9 mm Waters NovaPak C-18 4 μ packing

Detection=Activity=g and b⁻ scintillation detection (Packard Canberra Radiomatic 150TR scintillation analyser)

System G

Gilson 715 control software.

Isocratic; 18% B, 82% A

Eluent A=Na phosphate buffer (pH 6, 0.05M)

Eluent B=Acetonitrile

Flowrate=3 ml/min

Column=150×10.0 mm Chromtech Chiral AGP

Detection=UV (I=254 nm)

System H

Gilson 715 Software

Gradient=T_(0′)=100% A, 0% B, T_(20′)=0% A, 100% B

Eluent A=0.1% TEA in H₂O

Eluent B=0.1% TEA in MeCN

Flow rate=3 ml/min

Column=305×7 mm Hamilton PRP-1, 10 μ packing

Detection=UV (I=254 nm)

System I

Gilson 715 Software

Gradient=T_(0′)=100% A, T_(30′)=60% A, 40% B, T_(40′)=0% A, 100% B

Eluent A=2% NH₃ in H₂O

Eluent B=2% NH₃ in MeCN

Flow rate=3 ml/min

Column=305×7 mm Hamilton PRP-1, 10 μ packing

Detection=U.V. (I=210 nm)

System J

Gilson Unipoint Software

Gradient=T_(0′)=50% A, 50% B, T_(15′)=0% A, 100% B

Eluent A=0.2% TEA in H₂O

Eluent B=0.2% TEA in MeCN

Flow rate=3 ml/min

Column=NovaPak C18, 7.8×300 mm

Detection=U.V. (I=254 nm)

System K

Gilson 715 Software

Gradient=T_(0′)=70% A, 30% B, T_(20′)=0% A, 100% B

Eluent A=0.2% TEA in H₂O

Eluent B=0.2% TEA in MeCN

Flow rate=3 ml/min

Column=NovaPak C18, 7.8×300 mm

Detection=UV (I=254 nm)

TABLE 1 ¹H NMR Data for Compounds 2,3,4 and 5.

NMR data (ppm) Compound 2 Compound 3 Compound 4 Compound 5 CH₂CH₃ 0.93-1.10 0.91-1.16 0.93-1.08 0.80-1.71 CH₂CH₃ 1.55, 1.65-2.19 1.60-2.10 1.72-1.86 1.70-1.90 CH₂N 4.40 4.40-4.58 4.35-4.50 4.45-4.56 4-H 5.76 5.80 5.68 5.68 NH 6.85-6.96 6.90-7.00 6.85-7.00 6.90-7.00 Ar 7.07, 7.20, 7.08, 7.22, 7.00-7.13, 7.10-7.43 7.68, 7.98 7.65, 8.03 7.13-7.35, 7.35-7.50, 7.63-7.78 R₁ = Ot-Bu 1.55 R₁ = 2.30 (NCH₃), 2.31 (4-methyl- 2.30-2.60 (NCH₃), piperazinyl) (CH₂NCH₃), 2.31-3.50 3.40-3.90 (CH₂NCH₃) (CH₂NCO) 3.25-3.90 (CH₂NCO) R₂ = 0.80-1.71 Sn(n-Bu)₃

TABLE 2 ¹H NMR Data for Compounds 1,6,7,8 and 9.

NMR data (ppm) Compound 1 Compound 6 Compound 7 Compound 8 Compound 9 CH₂R₄ 4.45 2.64-2.76 2.73 2.84-2.92 2.78-2.93 CH₂Ar 3.20-3.40 3.33 3.08-3.16 3.34-3.88 Ar 7.00-7.10, 7.70 6.80, 7.00 6.92, 7.10 6.98, 7.20 6.81-7.93 R₃ = OH 7.44 R₃ = OCH₂Ar 5.04 (CH₂), 5.08 (CH₂), 5.06 (CH₂), 7.32-7.44 7.28-7.44 6.81-7.93 (Ar) (Ar) (Ar) R₄ = NHCO₂t-Bu 1.48 (t-Bu), 1.43 (t-Bu), 4.76 (NH) 4.54 (NH)

TABLE 3 ¹H NMR Data for Compounds 10 and 11.

NMR data (ppm) Compound 10 Compound 11 OCH₃ 3.32 3.20-3.28 CH₂O 3.60 3.20-3.28 CH₂R₅ 4.16 2.40 R₅ = OTs (ArCH₃) 2.45 (CH₃), 7.38 and 7.80 (Ar) R₅ = Ph₃CS 7.20-7.44

TABLE 4 ¹H NMR Data for Compound 12.

NMR data (ppm) Compound 12 CH₂CH₃ 0.90-1.10 CH₂CH₃ 1.60-1.92 CH₂ × 2 2.74-2.84 and 3.49-3.68 OCH₃ 3.38 4-H 4.49 NH 6.58

TABLE 5 ¹H NMR data for Compounds 18 and 19

NMR data (ppm) Compound 18 Compound 19 CH₃ 0.94 0.92 (CH₂)₂ 1.19-2.08 1.24-1.86 CHR₁₀ 3.52 4.57 Ar 7.17, 7.44 7.17, 7.48

TABLE 6 ¹H NMR data for Compounds 13,14,15,16 and 17.

NMR data (ppm) Compound 13 Compound 14 Compound 15 Compound 16 Compound 17 CH₂CH₃ 0.96 0.99-1.10 0.98-1.10 1.00-1.10 0.90-1.00 CH₂CH₃ 1.04, 1.66-2.40 1.63-2.40 1.40-1.60 1.60-2.40 1.67-1.90 CH₂Ar 2.75 2.80 2.76 2.70 2.60-2.70 XCH₂CH₂ 3.20, 3.09, 3.08-3.16, 3.00-3.10, 3.00-3.10, 3.25-3.72 3.70-3.76, 3.67-3.76, 3.70-3.78, 3.60-3.70, 3.91-4.00, 3.90-4.00, 3.90-4.00, 3.90-4.00, 4.53 4.41-4.57 4.40-4.60 4.50-4.60 CH₂N 3.25-3.72 3.40-3.53 3.43-.51 3.40-3.50 3.40-3.50 OCH₃ 3.25-3.72 3.40-3.53 3.40 3.40-3.50 3.40 4-H 5.00-5.04 5.11 5.11 5.10 5.10 NH 6.63 6.65 6.67 6.67 6.60 Ar 6.92, 7.13 6.93, 7.12 6.78, 7.03 6.90, 7.07, 7.45 7.50 R₇ = 5.00-5.04 5.04 (CH₂), OCH₂Ar (CH₂), 7.32-7.42 7.29-7.46 (Ar) (Ar) R₇ = OH 5.37

TABLE 7 ¹H NMR data for Compounds 20, 21, 22 and 23

NMR data Compound Compound Compound Compound (ppm) 20 21 22 23 CH₃ × 3 0.83-1.05 0.89-1.06 0.89-1.08 0.87-1.66 CH₂ 1.22-1.41 1.19-1.39 1.24-1.40 0.87-1.66 CH₂ × 3 1.68-2.05 1.66-2.06 1.68-2.06 1.71-2.03 CHNH 4.79 4.81 4.79 4.85 4-H 5.65 5.73 5.61 5.60 NH 6.89 6.92 6.94 6.97 Ar 7.16, 7.44, 7.13-7.23, 7.16, 7.24, 7.21-7.50 7.94 7.48, 8.05 7.38, 7.47 R₁₁ = Ot-Bu 1.59 R₁₁ = OH 7.62 R₁₁ = (4- 2.31 (CH₃), 2.31 (CH₃), methyipipera- 2.40 (CH₂), 2.40 (CH₂), zinyl) 3.71 (CH₂) 3.58-3.87 (CH₂) R₁₂ = Sn(n- 0.87-1.66 Bu)₃

TABLE 8 ¹H NMR data for compound 25

NMR data (ppm) Compound 25 CH₃ × 2 0.95-1.09 CH₂ × 2 1.71-2.00 4-H 5.36 Pyr 7.27, 8.27 NH 7.26

TABLE 9 ¹H NMR data for Compounds 29, 30, 31 and 35

Compound Compound Compound Compound NMR data 29 30 31 35 CH₂R₁₅ 4.37 4.34-4.35 4.13 4.50 Ar 7.37, 8.05 7.32-7.45, 7.30-7.44, 7.25-7.42, 8.03 7.96 8.01 R₁₄ = 5.34 (CH₂), 5.29 (CH₂), 5.31 (CH₂), CO₂CH₂Ar 7.32-7.45 7.30-7.44 7.25-7.42 (Ar) (Ar) (Ar) R₁₅ = NHCO₂t- 1.45 (t-Bu), 1.42 (t-Bu), Bu 4.93 (NH) 4.92 (NH)

TABLE 10 ¹H NMR data for compounds 26 and 27

NMR data (ppm) Compound 26 Compound 27 CH₃ × 2 0.84-2.04 0.86-1.58 CH₂ × 2 0.84-2.04 1.72-2.09 CH₂CH₂CH₃ 0.84-2.04 1.58-0.86 (CH₃ + CH₂), 1.72-2.09 (CH₂) CHNH 4.78 4.81 4-H 5.55 5.54 NH 6.91-7.49 6.94 Ar 6.91-7.49 7.21-7.28, 7.42 Pyr 6.91-7.49, 7.73, 8.31-8.44 7.21-7.28, 7.78, 8.33, 8.44 R₁₃ = Sn(n-Bu)₃ 0.86-1.58

TABLE 11 ¹H NMR data for compounds 32 and 33

NMR data (ppm) Compound 32 Compound 33 NCH₃ 2.28 2.33 2 × CH₂NCH₃ 2.38-2.46 2.48 2 × CH₂NCO 3.54-3.75 3.63 Ar 6.97, 7.30-7.45 6.84, 7.28 R₁₆ = OCH₂Ar 5.08 (CH₂), 7.30-7.45 (Ar) R₁₆ = OH 4.88

TABLE 12 ¹H NMR data for compound 34

NMR data (ppm) Compound 34 CH₃ × 2 1.02-1.11 CH₂ × 2 1.72-2.00 NCH₃ 2.33 2 × CH₂NCH₃ 2.44 2 × CH₂NCO 3.44-3.81 4-H 5.35 NH 6.78 Ar 6.87, 7.39

TABLE 13 ¹H NMR data for compounds 36, 37 and 38

NMR data (ppm) Compound 36 Compound 37 Compound 38 CH₃ × 2 0.90-1.02 0.98-1.09 0.97-1.08 CH₂ × 2 1.68-1.98 1.79-2.00 1.73-2.03 NCH₃ 2.25 2.63 2.32 2 × CH₂NCH₃ 2.33 2.88 2.42 2 × CH₂NCO 3.33-3.77 3.93-4.06 3.45-3.83 NCH₂Ar 4.47 4.54 4.52 4-H 5.63 5.71 5.68 urea NH 6.92 7.04 7.00 Ar 7.17, 7.25-7.37, 7.28, 7.37-7.43, 8.04 7.25, 7.33-7.42, 7.75 7.97 R₁₇ = OCH₂Ar 5.28 (CH₂), 7.25-7.37 (Ar) R₁₇ = Ligand 1 0.92 (CH₃), 1.23

(CH₃x4), 1.75 (CH₃x2), 2.18-2.37 (CH₂x2), 3.38 (CH₂), 8.37 (amide NH)

TABLE 14 ¹H NMR data for Compound 39

NMR data (ppm) Compound 39 CH₂CO₂ 2.58 CH₂N 3.51 CH₂Ar 5.17 Ar 7.36

TABLE 15 ¹H NMR data for Compounds 43, 44 and 45

NMR data (ppm) Compound 43 Compound 44 Compound 45 CH₂ x 3 1.21-1.71 1.34-1.73 1.40-1.80 CH₂CO₂ 2.35 2.41 2.45 CH₂R₁₉ 3.08 2.90 3.35 CH₂Ar 5.10 5.11 5.68 Ar 7.30 7.36 7.18-7.33 R₁₉ = NHCO₂t-Bu 1.46 (t-Bu), 4.46 (NH)

TABLE 16 ¹H NMR data for Compounds 40, 41, 42 and 51

NMR data Compound 40 Compound 41 Compound 42 Compound 51 2 x CH₃ 0.94-1.04 0.95-1.06 0.94-1.07 0.95-1.06 2 x CH₂ 1.71-1.97 1.76-1.99 1.67-2.01 1.79-2.01 NCH₃ 2.34 2.45 2.33 2.33 2 x CH₂NCH₃ 2.44-2.56 2.72 2.20-2.49 2.46-2.58 CH₂CO 2.61 2.54 2.20-2.49 2.46-2.58 CH₂NCON 3.51 3.54 3.49-3.72 3.21-3.83 2 x CH₂NCO 3.49-3.70 3.78 3.49-3.72 3.21-3.83 4-H 5.85 5.75 5.67 5.65 urea NH 7.20 7.07 7.14 Ar 7.23-7.43 7.25, 7.41 7.25, 7.40 7.22, 7.39 R₁₈ = 5.10 (CH₂), OCH₂Ar 7.23-7.43 (Ar) R₁₈ = OH 10.78 R₁₈ =

0.84 (CH₃), 1.22 (CH₃x4), 1.84 (CH₃x2), 2.20-2.49 (CH₂x2), 3.20 (CH₂), 7.79 (amide NH) R₁₈ =

1.25 (CH₃x4), 1.83 (CH₂x2), 2.46-2.58 (CH₂x5), 3.21- 3.83 (CH₂)

TABLE 17 ¹H NMR data for Compounds 46, 47 and 48

Compound Compound Compound NMR data (ppm) 46 47 48 CH₃CH₂ x 2 0.88-1.02 0.95-1.07 0.89-1.01 CH₂ x 3 1.25-1.65 1.30-1.68 1.25-1.60 CH₃CH₂ x 2 1.69-1.98 1.72-2.02 1.67-1.95 NCH₃ 2.23 2.37 2.25 CH₂NCH₃ x 2 2.29-2.46 2.55 2.35 CH₂CO 2.29-2.46 2.32 2.00-2.21 CH₂NCON 3.21 3.18-3.33 3.19-3.25 CH₂NCO x 2 3.35-3.79 3.50-3.88 3.49-3.76 4-H 5.60 5.65 5.57 NH 6.52 6.55 6.52 Ar 7.19, 7.23-7.38 7.23, 7.37 7.17, 7.32 R₂₀ = OCH₂Ar 5.04 (CH₂), 7.23-7.38 (Ar) R₂₀ = Ligand1

0.79 (CH₃), 1.18 (CH₃x4), 1.75 (CH₃x2), 2.00-2.21 (CH₂x2), 3.09 (CH₂)

TABLE 18 ¹H NMR data for Compounds 49 and 52

Compound Compound NMR data (ppm) 49 52 CH₂CH₃ x 2 0.90-1.26 0.94-1.11 CH₂CH₃ x 2 1.66-1.91 1.69-2.01 CH₂Ar 4.41 4.48 4-H 5.66 5.71 NH 6.84 6.90 Ar 7.16-7.31, 7.18, 7.22- 7.67 7.36, 7.82 R₂₁ = Ligand1

0.84 (CH₃), 2.19 (CH₃ x 4), 1.69 (CH₃ x 2), 1.95-2.19 (CH₂ x 2), 3.33 (CH₂), 9.72 (OH x 2) R₂₁ = Ligand2

1.14 (CH₃ x 4), 1.80 (CH₃ x 2), 2.55-2.76 (CH₂ x 5), 3.63 (CH₂)

TABLE 19 NMR data for compound 50

NMR data (ppm) Compound 50 4 x CH₃ 1.05 2 x CH₃ 1.71 6 x CH₂ 2.25-2.64

TABLE 20 RCP of ¹²³I-compounds before and after testing Pre-testing Post-testing Time Retention Time Retention Compound (min) time (min) RCP (min) time (min) RCP [¹²³I]-4 119  7.6 >95% 166 7.6 >90% [¹²³I]-4a — — — 371 ca 14.0⁽¹⁾ >95% [¹²³I]-4b — — — 428 ca 18.0⁽¹⁾ >95% [¹²³I]-16 101 17.3 >95% 154 17.3 >95% [¹²³I]-17 111 19.1 >95% 304 19.0 >95% ⁽¹⁾significant variation in retention time observed according to ambient HPLC conditions

TABLE 21 HPLC retention times (t_(R)) for ¹²³I and ¹²⁷I analogues t_(R) ¹²³I compound⁽¹⁾ t_(R) ¹²⁷I compound⁽¹⁾ Compound (g-detector) (min) (UV detector) (min)  4  6.6  6.4 16 17.3 17.1 17 19.1 18.9 ⁽¹⁾difference in t_(R) due to void volume differences

TABLE 22 RCP of ^(99m)Tc-labelled compounds before testing Time (min) after HPLC Compound purification Retention time (min) RCP ^(99m)Tc-38 60 15.5 >85% ^(99m)Tc-42 30 14.1 >85% ^(99m)Tc-48 60 15.1 >85% ^(99m)Tc-49 30 18.3 >85% ^(99m)Tc-51 60 12.5 >85% ^(99m)Tc-52 60 17.1 >85%

Example 13 Measurement of HLE Inhibition Potency

Inhibitor potency against HLE is described by the parameter k_(inact)/K_(i) as previously reported [Knight et al., Biochem., 8160-8170, (1992)]. Lyophilised enzyme was reconstituted with TrisHCl buffer, 100 mM, 0.5M NaCl at 0.05 units/ml (approximately nanomolar concentration) in a final reaction volume of 1 ml to which was added methoxysucc-ala-ala-pro-val-pNA substrate (1 mM) and the elastase inhibitor dissolved in DMSO. The reaction was monitored by detecting the change of absorbance at 410 nm (hydrolysis of the substrate releasing p-nitroaniline) over a timescale of 25 minutes. Values of k_(inact)/K_(i) were estimated according to the Knight et al method.

Results are given in Tables 23 and 24.

Example 14 Measurement of In Vitro Human Cell Selectivity in Isolated White Blood Cells, in Mixed White Plus Red Cells and in Whole Blood

Isolated Human White Cells

Fresh blood (30-120 ml) was anticoagulated with 1.5% ACD solution and sedimented by addition of 2 ml Hespan per 10 ml blood for 90 minutes at room temperature. The leucocyte rich platelet rich plasma supernatant was removed and centrifuged at 150 g for 5 minutes, yielding a leucocyte rich pellet and platelet rich plasma (PRP). The PRP was centrifuged at 4000 g to pellet the platelets leaving a cell free plasma (CFP). The leucocyte pellet was resuspended in a 50:50 mixture of HBSS and CFP and incubated with the radioactive compound for 30 minutes at 37° C. Free radioactive material was then removed from the cells by addition of an excess of HBSS:CFP and centrifugation of the leucocytes at 150 g for 7 minutes. The supernatant and cell pellet were taken for radioactive counting for calculation of percentage cell uptake. The distribution of radioactivity within the cell pellet was assessed by separation of the cell types using Percoll density gradient centrifugation (38%, 55% and 73% Percoll in HBSS step gradients). The residual plasma and free activity was recovered from the top of the gradient, the mononuclear cells (lymphocytes and monocytes) from the interface between 38% and 55%, and the granulocytes were recovered from the interface between 55% and 73% Percoll. Results are given in Table 23.

Mixed Human Red/White Cells.

The radioactive compound was also incubated with an isolated leucocyte preparation to which an erythrocyte fraction had been added back. The packed erythrocytes obtained after blood sedimentation were washed twice with HBSS and then resuspended in their original blood volume with HBSS. Leucocytes obtained from 30 ml blood were resuspended in 0.5 ml erythrocyte suspension and 0.5 ml CFP. The cell suspension was then incubated with compound as above. Analysis of the distribution of activity in the cell pellet in the presence of red blood cells was carried out using Ficoll-Hypaque discontinuous density gradients (densities 1.04, 1.077 and 1.119 g/ml Histopaque steps). Results are given in Table 23.

Human Whole Blood.

The radioactive compound was added to 1 ml whole blood anticoagulated with ACD and incubated at 37° C. for 1 hour. The blood was diluted with HBSS and the cellular component separated by centrifugation. Distribution of activity within the cellular pellet was assessed by separation of cell fractions on Ficoll-Hypaque gradients as above. Results are given in Table 23.

TABLE 23 Comparison of potency with in vitro human blood cell uptake WHITE AND Potency WHITE CELLS RED CELLS WHOLE BLOOD Compound (M/sec) Mon. Gran. Mon. Gran. Eryth. Mon. Gran. Eryth.  4 32,000 2.0 25.7  3.4 14.4  14.2  3.9 5.0 6.5  4a 63,000 14.3  68.6  14.6  53.2  8.4 — — —  4b   1350 0.9 4.8 3.8 3.3 1.6 — — — 16  2,700 0.0  0.55 0.6 0.3 0.6 0.6 0.2 0.2 17   600 0.0 0.4 — — — — — — 24  2830000  3.4 83.2  4.0 40.4  41.7  13.6  24.3  16.6  28  650000  14.8  67.4  14.9  41.9  17.5  — — — 38  58500 8.5 75.5  6.7 32.5  28.4  — — — 42   1400 1.2 8.4 6.9 2.5 18.9  — — — 48   5500 7.3 64.5  7.2 16.2  38.7  22.7  10.6   9.17 49  20000 10.1  47.3  13.9  17.5  18.0  24.6  6.9 14.3  51   2500 0.4 3.9 13.4  1.9 11.2  28.7  1.7 0.8 52   7800 0.8 1.9 8.2 1.8 7.1 10.9  9.1 37.4  where: Mon. = monocytes + lymphocytes Gran. = granulocytes Eryth. = erythrocytes Figures are % uptake in each cell fraction

Example 15 In Vivo Biodistribution of Radiolabelled Elastase Inhibitors in Rats Bearing Experimental Abscesses

The model: into the right gracilis (thigh) muscle of male Wistar rats (250-325 g) were injected 1 ml/kg of an E. coli suspension containing >> 5×10⁸/ml organisms. Over the next 24 hours a pustulent abscess developed at the site of the popliteum lymph node with the surrounding muscle also showing signs of inflammation. These visible observations were confirmed by histology.

Validation: the model was validated for use in the development of diagnostic imaging agents of infection/inflammation by the intravenous injection of ^(99m)Tc-HMPAO ex-vivo labelled human wbc or ⁶⁷Ga-citrate when the abscesses were 24 hours old. Animals were dissected between 4 and 24 hours after injection. ^(99m)Tc-labelled red blood cells were used as a negative control.

Screening in E. coli infected rats: 0.2-10 MBq of either ¹²³I- or ^(99m)Tc-labelled elastase inhibitors diluted in phosphate buffered saline (pH=7.4) were injected intravenously into the caudal vein of 24 hour abscess bearing rats. The animals were sacrificed at either 4 or 24 hours post injection and relevant tissues dissected.

Screening of Ex vivo labelled human leucocytes in E. coli infected rats: A mixed population of human leucocytes was incubated with elastase inhibitor for 30 minutes at 37° C. The cells were then spun down and resuspended in a known volume of rat plasma for intravenous injection into rats bearing a 24 hour old abscess. Animals were dissected at 4 and 24 hours post injection. Results are shown in Table 24.

Example 16 In Vivo Stability of Iodinated HLE Inhibitors

The in vivo stability of radioiodinated HLE inhibitors was monitored by determination of the percentage uptake in the thyroid as a function of time after administration. Thus radioiodinated compounds and ¹²³I free iodide were injected into male Wistar rats. The percentage of injected dose distributing to the thyroid was calculated by dissection at 4 and 24 hours post injection and counting. Results are given in Table 25.

Example 17 In-vitro Forming Plasma Clot Assay

1 μM of a potent (K_(inact)/K_(i)>3000000 M/sec) β-lactam elastase inhibitor was added to aliquots of human plasma pooled from 6 volunteers. The test sample contained plasma with added granulocytes (see example 14 for isolation method) to a final concentration of 10⁶/ml and 2 volumes of 50 mM Tris buffered saline containing 15 mM calcium chloride. The control sample consisted of plasma and Tris buffer without calcium. Clots were allowed to form for 60 minutes after the addition of 4 units of bovine thrombin and a roughened glass rod to induce clot formation.

After incubation (c.20° C.) the reaction was discontinued by the addition of 400 μL cold 33.5mM ethylenediaminetetraacetic acid disodium salt. Solutions were filtered by the use of a vacuum manifold onto 0.45 μm nitrocellulose filters (pre-soaked in 1.5% bovine serum albumin/Tris buffered saline, pH 7.5 containing 0.1% Tween 20) and washed with the same buffer minus BSA.

The fraction of radioactivity retained on the filter, after subtraction of non-specific binding is a measure of % incorporation into the filtered clots.

TABLE 24 Screening of elastase inhibitors by direct intravenous injection and injection of ex vivo labelled human leucocytes k_(inact)/Ki Relative conc. Compound (human elastase) Infected/normal Infected/blood In infected area Directly injected 32000  4 hrs 1.3  4 hrs 0.62  4 hrs 0.51 [¹²³I]-4 24 hrs 1.3 24 hrs 0.51 24 hrs 0.12 Directly injected 36000  4 hrs 1.0  4 hrs 0.62  4 hrs 0.52 [¹²³I]-4a 24 hrs 1.6 24 hrs 0.53 24 hrs 0.28 Ex vivo labelled 32000  4 hrs 1.5  4 hrs 0.61  4 hrs 0.7  [¹²³I]-4 24 hrs 1.9 24 hrs 0.75 24 hrs 0.19 Directly injected 2830000   4 hrs 1.3  4 hrs 1.3  4 hrs 0.38 [¹²³I]-24 24 hrs 1.1 24 hrs 0.9 24 hrs 0.16 Ex vivo labelled 2830000   4 hrs 1.3  4 hrs 0.9  4 hrs 0.53 [¹²³I]-24 24 hrs 1.3 24 hrs 0.9 24 hrs 0.20 Directly injected 650000   4 hrs 1.3  4 hrs 1.1  4 hrs 0.22 [¹²³I]-28 24 hrs 1.2 24 hrs 1.2 24 hrs 0.12 Ex vivo labelled 650000   4 hrs 1.5  4 hrs 0.9  4 hrs 0.45 [¹²³I]-28 24 hrs 1.2 24 hrs 0.9 24 hrs 0.16 Directly injected 58500  4 hrs 1.4  4 hrs 1.0  4 hrs 0.08 [^(99m)Tc]-38 24 hrs nc 24 hrs 1.4 24 hrs 0.14 Directly injected  1400  4 hrs 2.7  4 hrs 0.9  4 hrs 0.10 [^(99m)Tc]-42 24 hrs nc 24 hrs 2.2 24 hrs 0.11 Directly injected  5500  4 hrs 1.7  4 hrs 1.0  4 hrs 0.07 [^(99m)Tc]-48 24 hrs nc 24 hrs 2.5 24 hrs 0.08 Directly injected 20000  4 hrs 1.5  4 hrs 0.5  4 hrs 0.05 [^(99m)Tc]-49 24 hrs 2.0 24 hrs 1.5 24 hrs 0.16 Ex vivo labelled —  4 hrs 3.3  4 hrs 0.4  4 hrs 0.2  ^(99m)Tc HMPAO wbc 24 hrs 4.0 24 hrs 0.7 24 hrs 0.1  Directly injected —  4 hrs 0.6  4 hrs <0.01  4 hrs 0.1  ^(99m)Tc-RBC's 24 hrs 0.8 24 hrs <0.01 24 hrs 0.1  ⁶⁷Ga-citrate — 24 hrs 2.2 24 hrs 3.9 24 hrs 0.9  48 hrs 3.9 48 hrs 9.7 48 hrs 1.1  Parameters are defined as follows: 1) Infected/normal ratio: the ratio of the % injected dose identified (id) per gram of tissue in the infected area relative to that seen in a control area taken from the thigh of the contralateral limb. 2) Infected/blood ratio: the ratio of %/g in the infected area relative to activity in blood. A low ratio indicates that the accumulation in the infected area could be masked by the activity in the blood pool. 3) The relative concentration of agent in the infected area. This can be defined as the % of the injected dose in a % body weight. For example 1% of the injected dose in a tissue which is 1% of the body weight would have a relative concentration of 1.

TABLE 25 % Thyroid uptake following i.v. injection of free [¹²³I]- iodide and ¹²³I-labelled compounds % dose in Thyroid Compound 4 hours 24 hours [¹²³I]-iodide 6.8 22.2  [¹²³I]-4 0.1 0.9 [¹²³I]-4a 0.1 0.3 [¹²³I]-16 0.3 2.4 [¹²³I]-24 0.2 0.6 

What is claimed is:
 1. A human leucocyte elastase (HLE) inhibitor labelled with a detectable moiety where the inhibitor is synthetic and has a molecular weight of less than 2000, and the detectable moiety is chosen from the group consisting of a radioactive isotope, a paramagnetic ion, a radiopaque compound and an ultrasound contrast agent.
 2. The labelled HLE inhibitor of claim 1 where the radioactive isotope is a gamma emitter.
 3. The labelled HLE inhibitor of claim 1 where the radioactive isotope is ¹²³I, ^(99m)TC, ¹¹¹In or ⁶⁷Ga.
 4. The labelled HLE inhibitor of claim 1 where the inhibitor is β-lactam.
 5. The labelled HLE inhibitor of claim 1 where the inhibitor is an ynenol lactone.
 6. The labelled HLE inhibitor of claim 4 where the β-lactam has the general formula:

wherein R¹ is R⁸, XR⁸, (CRR)_(n)(C═X)R⁸ or (C═X)NR⁸ ₂ X is O or S n is O-3, R⁸ is H, OH, a substituted or unsubstituted C₃₋₁₂ carbocyclic or heterocyclic ring which may be saturated or unsaturated, C₁₋₁₀ alkyl, C₃₋₁₂ aryl, C₄₋₁₂ alkylaryl, C₂₋₁₀ alkenyl, C₂₋₁₀ alkynyl, C₁₋₁₀ alkoxy, C₁₋₁₀ alkoxyalkyl, C₁₋₁₀ hydroxyalkyl, C₁₋₁₀ aminoalkyl, C₁₋₁₀ perfluoroalkyl, C₁₋₁₀ haloalkyl, C₁₋₁₀ carboxyalkyl, C₁₋₁₀ amidoalkyl or C₁₋₁₀ ketoalkyl, R², R³ are the same or different and each H, C₁₋₄ alkyl, C₂₋₄ alkenyl, C₂₋₄ alkynyl, C₁₋₄ alkoxyalkyl, C₁₋₄ hydroxyalkyl, C₁₋₄ aminoalkyl, C₁₋₄ perfluoroalkyl, C₁₋₄ haloalkyl, Hal, C₁₋₄ carboxyalkyl, OR, SR, NRR, (CH₂)_(n)CONRR, NR(CO)R or (CH₂)_(n)CO₂R, R⁴ is a leaving group selected from the group consisting of halogen, XR⁸, X(C═X)R⁸, OSOR⁸, OSO₂R⁸ OSO₂Hal, SOR⁸, SO₂R⁸, SO₂NR⁸ ₂ NRSO₂R, (C═X)R⁸, (C═X)NR⁸ ₂, (C═X)R⁸, NO₂, CN, PO_(n)R⁸ ₂ or XC₆H_(4−n)Y_(n) Y is the same or different and is R, NO₂, Hal, CONR⁸ ₂, SO₂NR⁸ ₂ or CO₂R, R⁵ is R or R⁴ R is the same or different and is H, C₁₋₄ alkyl, C₂₋₄ alkenyl, C₂₋₄ alkynyl, C₁₋₄ alkoxy, C₁₋₄ alkoxyalkyl, C₁₋₄ hydroxyalkyl, C₁₋₄ aminoalkyl, C₁₋₄ perfluoroalkyl, C₁₋₄ haloalkyl or C₁₋₄ carboxyalkyl, whereby two or more of the groups R¹, R², R³, R⁴ and R⁵ may be combined to form a substituted or unsubstituted carbocyclic or heterocyclic ring which may be saturated or unsaturated, wherein the β-lactam contains or has covalently bonded thereto at least one detectable moiety, and with the proviso that when R⁴ is XR⁸, X is S and R¹ and R⁴ are combined to form a cyclic carboxyalkyl group, then the detectable moiety is not ¹²⁵I.
 7. The labelled HLE inhibitor of claim 4 where the inhibitor is an azetidinone.
 8. The labelled HLE inhibitor of claim 7 where the azetidinone has the formula:

wherein R¹ is R⁸, XR⁸, (CRR)_(n)(C═X)R⁸ or (C═X)NR⁸ ₂ X is O or S n is O-3, R⁸ is H, OH, a substituted or unsubstituted C₃₋₁₂ carbocyclic or heterocyclic ring which may be saturated or unsaturated, C₁₋₁₀ alkyl, C₃₋₁₂ aryl, C₄₋₁₂ alkylaryl, C₂₋₁₀ alkenyl, C₂₋₁₀ alkynyl, C₁₋₁₀ alkoxy, C₁₋₁₀ alkoxyalkyl, C₁₋₁₀ hydroxyalkyl, C₁₋₁₀ aminoalkyl, C₁₋₁₀ perfluoroalkyl, C₁₋₁₀ haloalkyl, C₁₋₁₀ carboxyalkyl, C₁₋₁₀ amidoalkyl or C₁₋₁₀ ketoalkyl, R², R³ are the same or different and each H, C₁₋₄ alkyl, C₂₋₄ alkenyl, C₂₋₄ alkynyl, C₁₋₄ alkoxyalkyl, C₁₋₄ hydroxyalkyl, C₁₋₄ aminoalkyl, C₁₋₄ perfluoroalkyl, C₁₋₄ haloalkyl, Hal, C₁₋₄ carboxyalkyl, OR, SR, NRR, (CH₂)_(n)CONRR, NR(CO)R or (CH₂)_(n)CO₂R, R⁴ is a leaving group selected from the group consisting of halogen, XR⁶, X(C═X)R⁸, OSOR⁸, OSO₂R⁸ OSO₂Hal, SOR⁸, SO₂R⁸, SO₂NR⁸ ₂ NRSO₂R, (C═X)R⁸, (C═X)NR⁸ ₂, (C═X)R⁸, NO₂, CN, PO_(n)R⁸ ₂ or XC₈H_(4−n), Y is the same or different and is R, NO₂, halogen, CONR⁸ ₂, SO₂NR⁸ ₂ or CO₂R, R⁵ is R or R⁴ R is the same or different and is H, C₁₋₄ alkyl, C₂₋₄ alkenyl, C₂₋₄ alkynyl, C₁₋₄ alkoxy, C₁₋₄ alkoxyalkyl, C₁₋₄ hydroxyalkyl, C₁₋₄ aminoalkyl, C₁₋₄ perfluoroalkyl, C₁₋₄ haloalkyl or C₁₋₄ carboxyalkyl, wherein the azetidinone contains or has covalently bonded thereto at least one detectable moiety.
 9. The labelled HLE inhibitor of claim 8 where the detectable moiety is attached at the R₁ position.
 10. The labelled HLE inhibitor of claim 8 where at least one of the groups R₁₋₅ bears an amine substituent.
 11. A method for detecting a site of inflammation in vivo comprising: administering the labelled HLE inhibitor of claim 1; detecting the presence of the HLE inhibitor at a site of inflammation.
 12. A method for labelling leucocytes in vitro comprising: combining leucocytes and the labelled HLE inhibitor of claim
 1. 13. A method for imaging thromb in vivo comprising: administering the labelled HLE inhibitor of claim 1; detecting radiation emitted by the labelled HLE inhibitor that has accumulated at a thromb and generating an image therefrom.
 14. A method for treating arthritis, bone infection or other hyperproliferative disease with radiation, the method comprising: administering the labelled HLE inhibitor of claim
 1. 